Thursday, November 4, 2010

sql queries

T-SQL Queries

1. 2 tables

Employee Phone

empid

empname

salary

mgrid empid

phnumber



2. Select all employees who doesn't have phone?

SELECT empname

FROM Employee

WHERE (empid NOT IN

(SELECT DISTINCT empid

FROM phone))





3. Select the employee names who is having more than one phone numbers.

SELECT empname

FROM employee

WHERE (empid IN

(SELECT empid

FROM phone

GROUP BY empid

HAVING COUNT(empid) > 1))



4. Select the details of 3 max salaried employees from employee table.

SELECT TOP 3 empid, salary

FROM employee

ORDER BY salary DESC



5. Display all managers from the table. (manager id is same as emp id)

SELECT empname

FROM employee

WHERE (empid IN

(SELECT DISTINCT mgrid

FROM employee))



6. Write a Select statement to list the Employee Name, Manager Name

under a particular manager?

SELECT e1.empname AS EmpName, e2.empname AS ManagerName

FROM Employee e1 INNER JOIN

Employee e2 ON e1.mgrid = e2.empid

ORDER BY e2.mgrid



7. 2 tables emp and phone.

emp fields are - empid, name

Ph fields are - empid, ph (office, mobile, home). Select all employees

who doesn't have any ph nos.

SELECT *

FROM employee LEFT OUTER JOIN

phone ON employee.empid = phone.empid

WHERE (phone.office IS NULL OR phone.office = ' ')

AND (phone.mobile IS NULL OR phone.mobile = ' ')

AND (phone.home IS NULL OR phone.home = ' ')



8. Find employee who is living in more than one city.

Two Tables:

Emp City

Empid Empid

empName City

Salary

SELECT empname, fname, lname

FROM employee

WHERE (empid IN

(SELECT empid

FROM city

GROUP BY empid

HAVING COUNT(empid) > 1))

9. Find all employees who is living in the same city. (table is same

as above)

SELECT fname FROM employee WHERE (empid IN (SELECT empid

FROM city a mWHERE city IN (SELECT city

FROM city b GROUP BY city

HAVING COUNT(city) > 1)))n 10. There is a table named MovieTable with three columns - moviename, person and role. Write a query which gets the movie details where Mr. Amitabh and Mr. Vinod acted and their role is actor.

SELECT DISTINCT m1.moviename

FROM MovieTable m1 INNER JOIN

MovieTable m2 ON m1.moviename = m2.moviename

WHERE (m1.person = 'amitabh' AND m2.person = 'vinod' OR

m2.person = 'amitabh' AND m1.person = 'vinod') AND (m1.role = 'actor')

AND (m2.role = 'actor')

ORDER BY m1.moviename

11. There are two employee tables named emp1 and emp2. Both contains same structure (salary details). But Emp2 salary details are incorrect and emp1 salary details are correct. So, write a query which corrects salary details of the table emp2 update a set a.sal=b.sal from emp1 a, emp2 b where a.empid=b.empid 12. Given a Table named "Students" which contains studentid, subjected and marks. Where there are 10 subjects and 50 students. Write a Query to find out the Maximum marks obtained in each subject.

13. In this same tables now write a SQL Query to get the studentid

also to combine with previous results.



14. Three tables – student , course, marks – how do go @ finding name of the students who got max marks in the diff courses.

SELECT student.name, course.name AS coursename, marks.sid, marks.mark

FROM marks INNER JOIN

student ON marks.sid = student.sid INNER JOIN

course ON marks.cid = course.cid

WHERE (marks.mark =

(SELECT MAX(Mark)

FROM Marks MaxMark

WHERE MaxMark.cID = Marks.cID))



15. There is a table day_temp which has three columns dayid, day and temperature. How do I write a query to get the difference of temperature among each other for seven days of a week?

SELECT a.dayid, a.dday, a.tempe, a.tempe - b.tempe AS DifferenceFROM day_temp a INNER JOIN

day_temp b ON a.dayid = b.dayid + 1

OR

Select a.day, a.degree-b.degree from temperature a, temperature bwhere a.id=b.id+1



16. There is a table which contains the names like this. a1, a2, a3,a3, a4, a1, a1, a2 and their salaries. Write a query to get grand total salary, and total salaries of individual employees in one query.

SELECT empid, SUM(salary) AS salary FROM employee

GROUP BY empid WITH ROLLUP ORDER BY empid

17. How to know how many tables contains empno as a column in a database?

SELECT COUNT(*) AS Counter

FROM syscolumns

WHERE (name = 'empno')

18. Find duplicate rows in a table? OR I have a table with one column

which has many records which are not distinct. I need to find the

distinct values from that column and number of times it's repeated.

SELECT sid, mark, COUNT(*) AS Counter

FROM marks

GROUP BY sid, mark

HAVING (COUNT(*) > 1)

19. How to delete the rows which are duplicate (don't delete both

duplicate records).

SET ROWCOUNT 1

DELETE yourtable

FROM yourtable a

WHERE (SELECT COUNT(*) FROM yourtable b WHERE b.name1 = a.name1 AND

b.age1 = a.age1) > 1

WHILE @@rowcount > 0

DELETE yourtable

FROM yourtable a

WHERE (SELECT COUNT(*) FROM yourtable b WHERE b.name1 = a.name1 AND

b.age1 = a.age1) > 1

SET ROWCOUNT 0



20. How to find 6th highest salary

SELECT TOP 1 salary

FROM (SELECT DISTINCT TOP 6 salary

FROM employee

ORDER BY salary DESC) a

ORDER BY salary



21. Find top salary among two tables

SELECT TOP 1 sal

FROM (SELECT MAX(sal) AS sal

FROM sal1

UNION

SELECT MAX(sal) AS sal

FROM sal2) a

ORDER BY sal DESC



22. Write a query to convert all the letters in a word to upper case

SELECT UPPER('test')



23. Write a query to round up the values of a number. For example even

if the user enters 7.1 it should be rounded up to 8.

SELECT CEILING (7.1)



24. Write a SQL Query to find first day of month?



SELECT DATENAME(dw, DATEADD(dd, - DATEPART(dd, GETDATE()) + 1,

GETDATE())) AS FirstDay

Datepart Abbreviations

year yy, yyyy

quarter qq, q

month mm, m

dayofyear dy, y

day dd, d

week wk, ww

weekday dw

hour hh

minute mi, n

second ss, s

millisecond ms



25. Table A contains column1 which is primary key and has 2 values (1,

2) and Table B contains column1 which is primary key and has 2 values

(2, 3). Write a query which returns the values that are not common for

the tables and the query should return one column with 2 records.

SELECT a.col1

FROM a, b

WHERE a.col1 <>

(SELECT b.col1

FROM a, b

WHERE a.col1 = b.col1)

UNION

SELECT b.col1

FROM a, b

WHERE b.col1 <>

(SELECT a.col1

FROM a, b

WHERE a.col1 = b.col1)



26. There are 3 tables Titles, Authors and Title-Authors. Write the

query to get the author name and the number of books written by that

author, the result should start from the author who has written the

maximum number of books and end with the author who has written the

minimum number of books.



27.

UPDATE emp_master

SET emp_sal =

CASE

WHEN emp_sal > 0 AND emp_sal <= 20000 THEN (emp_sal * 1.01) WHEN emp_sal > 20000 THEN (emp_sal * 1.02)

END



FAQ on Indexes in SQL

FAQ on Indexes in SQL



28. What is Index? It's purpose?

Indexes in databases are similar to indexes in books. In a database,

an index allows the database program to find data in a table without

scanning the entire table. An index in a database is a list of values

in a table with the storage locations of rows in the table that

contain each value. Indexes can be created on either a single column

or a combination of columns in a table and are implemented in the form

of B-trees. An index contains an entry with one or more columns (the

search key) from each row in a table. A B-tree is sorted on the search

key, and can be searched efficiently on any leading subset of the



search key. For example, an index on columns A, B, C can be searched

efficiently on A, on A, B, and A, B, C.



29. Explain about Clustered and non clustered index? How to choose

between a Clustered Index and a Non-Clustered Index?

There are clustered and nonclustered indexes. A clustered index is a

special type of index that reorders the way records in the table are

physically stored. Therefore table can have only one clustered index.

The leaf nodes of a clustered index contain the data pages.

A nonclustered index is a special type of index in which the logical

order of the index does not match the physical stored order of the

rows on disk. The leaf nodes of a nonclustered index does not consist

of the data pages. Instead, the leaf nodes contain index rows.

Consider using a clustered index for:

o Columns that contain a large number of distinct values.

o Queries that return a range of values using operators such as

BETWEEN, >, >=, <, and <=. o Columns that are accessed sequentially. o Queries that return large result sets. Non-clustered indexes have the same B-tree structure as clustered indexes, with two significant differences: o The data rows are not sorted and stored in order based on their non-clustered keys. o The leaf layer of a non-clustered index does not consist of the data pages. Instead, the leaf nodes contain index rows. Each index row contains the non-clustered key value and one or more row locators that point to the data row (or rows if the index is not unique) having the key value. o Per table only 249 non clustered indexes. 30. Disadvantage of index? Every index increases the time in takes to perform INSERTS, UPDATES and DELETES, so the number of indexes should not be very much. 31. Given a scenario that I have a 10 Clustered Index in a Table to all their 10 Columns. What are the advantages and disadvantages? A: Only 1 clustered index is possible.





32. How can I enforce to use particular index?

You can use index hint (index=) after the table name.

SELECT au_lname FROM authors (index=aunmind)



33. What is Index Tuning?

One of the hardest tasks facing database administrators is the

selection of appropriate columns for non-clustered indexes. You should

consider creating non-clustered indexes on any columns that are

frequently referenced in the WHERE clauses of SQL statements. Other

good candidates are columns referenced by JOIN and GROUP BY operations.

You may wish to also consider creating non-clustered indexes that

cover all of the columns used by certain frequently issued queries.

These queries are referred to as "covered queries" and experience

excellent performance gains.

Index Tuning is the process of finding appropriate column for

non-clustered indexes.

SQL Server provides a wonderful facility known as the Index Tuning

Wizard which greatly enhances the index selection process.



34. Difference between Index defrag and Index rebuild?

When you create an index in the database, the index information used

by queries is stored in index pages. The sequential index pages are

chained together by pointers from one page to the next. When changes

are made to the data that affect the index, the information in the

index can become scattered in the database. Rebuilding an index

reorganizes the storage of the index data (and table data in the case

of a clustered index) to remove fragmentation. This can improve disk

performance by reducing the number of page reads required to obtain

the requested data

DBCC INDEXDEFRAG - Defragments clustered and secondary indexes of the

specified table or view.

**



35. What is sorting and what is the difference between sorting &

clustered indexes?

The ORDER BY clause sorts query results by one or more columns up to

8,060 bytes. This will happen by the time when we retrieve data from



database. Clustered indexes physically sorting data, while

inserting/updating the table.



36. What are statistics, under what circumstances they go out of date,

how do you update them?

Statistics determine the selectivity of the indexes. If an indexed

column has unique values then the selectivity of that index is more,

as opposed to an index with non-unique values. Query optimizer uses

these indexes in determining whether to choose an index or not while

executing a query.

Some situations under which you should update statistics:

1) If there is significant change in the key values in the index

2) If a large amount of data in an indexed column has been added,

changed, or removed (that is, if the distribution of key values has

changed), or the table has been truncated using the TRUNCATE TABLE

statement and then repopulated

3) Database is upgraded from a previous version



37. What is fillfactor? What is the use of it ? What happens when we

ignore it? When you should use low fill factor?

When you create a clustered index, the data in the table is stored in

the data pages of the database according to the order of the values in

the indexed columns. When new rows of data are inserted into the table

or the values in the indexed columns are changed, Microsoft® SQL

Server™ 2000 may have to reorganize the storage of the data in the

table to make room for the new row and maintain the ordered storage of

the data. This also applies to nonclustered indexes. When data is

added or changed, SQL Server may have to reorganize the storage of the

data in the nonclustered index pages. When a new row is added to a

full index page, SQL Server moves approximately half the rows to a new

page to make room for the new row. This reorganization is known as a

page split. Page splitting can impair performance and fragment the

storage of the data in a table.

When creating an index, you can specify a fill factor to leave extra



gaps and reserve a percentage of free space on each leaf level page of

the index to accommodate future expansion in the storage of the

table's data and reduce the potential for page splits. The fill factor

value is a percentage from 0 to 100 that specifies how much to fill

the data pages after the index is created. A value of 100 means the

pages will be full and will take the least amount of storage space.

This setting should be used only when there will be no changes to the

data, for example, on a read-only table. A lower value leaves more

empty space on the data pages, which reduces the need to split data

pages as indexes grow but requires more storage space. This setting is

more appropriate when there will be changes to the data in the table.



FAQ on Data Types in SQL Server

FAQ on Data Types in SQL Server



38. What are the data types in SQL

bigint Binary bit char cursor

datetime Decimal float image int

money Nchar ntext nvarchar real

smalldatetime Smallint smallmoney text timestamp

tinyint Varbinary Varchar uniqueidentifier



39. Difference between char and nvarchar / char and varchar data-type?

char[(n)] - Fixed-length non-Unicode character data with length of n

bytes. n must be a value from 1 through 8,000. Storage size is n

bytes. The SQL-92 synonym for char is character.

nvarchar(n) - Variable-length Unicode character data of n characters.

n must be a value from 1 through 4,000. Storage size, in bytes, is two

times the number of characters entered. The data entered can be 0

characters in length. The SQL-92 synonyms for nvarchar are national

char varying and national character varying.

varchar[(n)] - Variable-length non-Unicode character data with length

of n bytes. n must be a value from 1 through 8,000. Storage size is

the actual length in bytes of the data entered, not n bytes. The data

entered can be 0 characters in length. The SQL-92 synonyms for varchar

are char varying or character varying.



40. GUID datasize?



128bit



41. How GUID becoming unique across machines?

To ensure uniqueness across machines, the ID of the network card is

used (among others) to compute the number.



42. What is the difference between text and image data type?

Text and image. Use text for character data if you need to store more

than 255 characters in SQL Server 6.5, or more than 8000 in SQL Server

7.0. Use image for binary large objects (BLOBs) such as digital

images. With text and image data types, the data is not stored in the

row, so the limit of the page size does not apply.All that is stored

in the row is a pointer to the database pages that contain the

data.Individual text, ntext, and image values can be a maximum of

2-GB, which is too long to store in a single data row.

FAQ on Joins in SQL Server



43. What are joins?

Sometimes we have to select data from two or more tables to make our

result complete. We have to perform a join.



44. How many types of Joins?

Joins can be categorized as:

• Inner joins (the typical join operation, which uses some comparison

operator like = or <>). These include equi-joins and natural joins.

Inner joins use a comparison operator to match rows from two tables

based on the values in common columns from each table. For example,

retrieving all rows where the student identification number is the

same in both the students and courses tables.

• Outer joins. Outer joins can be a left, a right, or full outer join.

Outer joins are specified with one of the following sets of keywords

when they are specified in the FROM clause:

• LEFT JOIN or LEFT OUTER JOIN -The result set of a left outer join

includes all the rows from the left table specified in the LEFT OUTER

clause, not just the ones in which the joined columns match. When a

row in the left table has no matching rows in the right table, the

associated result set row contains null values for all select list

columns coming from the right table.



• RIGHT JOIN or RIGHT OUTER JOIN - A right outer join is the reverse

of a left outer join. All rows from the right table are returned. Null

values are returned for the left table any time a right table row has

no matching row in the left table.

• FULL JOIN or FULL OUTER JOIN - A full outer join returns all rows in

both the left and right tables. Any time a row has no match in the

other table, the select list columns from the other table contain null

values. When there is a match between the tables, the entire result

set row contains data values from the base tables.

• Cross joins - Cross joins return all rows from the left table, each

row from the left table is combined with all rows from the right

table. Cross joins are also called Cartesian products. (A Cartesian

join will get you a Cartesian product. A Cartesian join is when you

join every row of one table to every row of another table. You can

also get one by joining every row of a table to every row of itself.)



45. What is self join?

A table can be joined to itself in a self-join.



46. What are the differences between UNION and JOINS?

A join selects columns from 2 or more tables. A union selects rows.



47. Can I improve performance by using the ANSI-style joins instead of

the old-style joins?

Code Example 1:

select o.name, i.name

from sysobjects o, sysindexes i

where o.id = i.id

Code Example 2:

select o.name,

i.name

from sysobjects o inner join sysindexes i

on o.id = i.id

You will not get any performance gain by switching to the ANSI-style

JOIN syntax.

Using the ANSI-JOIN syntax gives you an important advantage: Because

the join logic is cleanly separated from the filtering criteria, you

can understand the query logic more quickly.

The SQL Server old-style JOIN executes the filtering conditions before

executing the joins, whereas the ANSI-style JOIN reverses this

procedure (join logic precedes filtering).

Perhaps the most compelling argument for switching to the ANSI-style

JOIN is that Microsoft has explicitly stated that SQL Server will not

support the old-style OUTER JOIN syntax indefinitely. Another

important consideration is that the ANSI-style JOIN supports query

constructions that the old-style JOIN syntax does not support.



48. What is derived table?

Derived tables are SELECT statements in the FROM clause referred to by

an alias or a user-specified name. The result set of the SELECT in the

FROM clause forms a table used by the outer SELECT statement. For

example, this SELECT uses a derived table to find if any store carries

all book titles in the pubs database:

SELECT ST.stor_id, ST.stor_name

FROM stores AS ST,

(SELECT stor_id, COUNT(DISTINCT title_id) AS title_count

FROM sales

GROUP BY stor_id

) AS SA

WHERE ST.stor_id = SA.stor_id

AND SA.title_count = (SELECT COUNT(*) FROM titles)

b

FAQ on Joins in SQL Server



43. What are joins?

Sometimes we have to select data from two or more tables to make our

result complete. We have to perform a join.



44. How many types of Joins?

Joins can be categorized as:

• Inner joins (the typical join operation, which uses some comparison

operator like = or <>). These include equi-joins and natural joins.

Inner joins use a comparison operator to match rows from two tables

based on the values in common columns from each table. For example,

retrieving all rows where the student identification number is the

same in both the students and courses tables.

• Outer joins. Outer joins can be a left, a right, or full outer join.

Outer joins are specified with one of the following sets of keywords

when they are specified in the FROM clause:

• LEFT JOIN or LEFT OUTER JOIN -The result set of a left outer join

includes all the rows from the left table specified in the LEFT OUTER

clause, not just the ones in which the joined columns match. When a

row in the left table has no matching rows in the right table, the

associated result set row contains null values for all select list

columns coming from the right table.



• RIGHT JOIN or RIGHT OUTER JOIN - A right outer join is the reverse

of a left outer join. All rows from the right table are returned. Null

values are returned for the left table any time a right table row has

no matching row in the left table.

• FULL JOIN or FULL OUTER JOIN - A full outer join returns all rows in

both the left and right tables. Any time a row has no match in the

other table, the select list columns from the other table contain null

values. When there is a match between the tables, the entire result

set row contains data values from the base tables.

• Cross joins - Cross joins return all rows from the left table, each

row from the left table is combined with all rows from the right

table. Cross joins are also called Cartesian products. (A Cartesian

join will get you a Cartesian product. A Cartesian join is when you

join every row of one table to every row of another table. You can

also get one by joining every row of a table to every row of itself.)



45. What is self join?

A table can be joined to itself in a self-join.



46. What are the differences between UNION and JOINS?

A join selects columns from 2 or more tables. A union selects rows.



47. Can I improve performance by using the ANSI-style joins instead of

the old-style joins?

Code Example 1:

select o.name, i.name

from sysobjects o, sysindexes i

where o.id = i.id

Code Example 2:

select o.name,

i.name

from sysobjects o inner join sysindexes i

on o.id = i.id

You will not get any performance gain by switching to the ANSI-style

JOIN syntax.

Using the ANSI-JOIN syntax gives you an important advantage: Because

the join logic is cleanly separated from the filtering criteria, you

can understand the query logic more quickly.

The SQL Server old-style JOIN executes the filtering conditions before

executing the joins, whereas the ANSI-style JOIN reverses this

procedure (join logic precedes filtering).

Perhaps the most compelling argument for switching to the ANSI-style

JOIN is that Microsoft has explicitly stated that SQL Server will not

support the old-style OUTER JOIN syntax indefinitely. Another

important consideration is that the ANSI-style JOIN supports query

constructions that the old-style JOIN syntax does not support.



48. What is derived table?

Derived tables are SELECT statements in the FROM clause referred to by

an alias or a user-specified name. The result set of the SELECT in the

FROM clause forms a table used by the outer SELECT statement. For

example, this SELECT uses a derived table to find if any store carries

all book titles in the pubs database:

SELECT ST.stor_id, ST.stor_name

FROM stores AS ST,

(SELECT stor_id, COUNT(DISTINCT title_id) AS title_count

FROM sales

GROUP BY stor_id

) AS SA

WHERE ST.stor_id = SA.stor_id

AND SA.title_count = (SELECT COUNT(*) FROM titles)

FAQ on Trigger in SQL Server

FAQ on Trigger in SQL Server



71. What is Trigger? What is its use? What are the types of Triggers?

What are the new kinds of triggers in sql 2000? When should one use

"instead of Trigger"?

Microsoft® SQL Serve 2000 triggers are a special class of stored

procedure defined to execute automatically when an UPDATE, INSERT, or

DELETE statement is issued against a table or view. Triggers are

powerful tools that sites can use to enforce their business rules

automatically when data is modified.

The CREATE TRIGGER statement can be defined with the FOR UPDATE, FOR

INSERT, or FOR DELETE clauses to target a trigger to a specific class

of data modification actions. When FOR UPDATE is specified, the IF

UPDATE (column_name) clause can be used to target a trigger to updates

affecting a particular column.

You can use the FOR clause to specify when a trigger is executed:

• AFTER - The trigger executes after the statement that triggered it

completes. If the statement fails with an error, such as a constraint

violation or syntax error, the trigger is not executed. AFTER triggers

cannot be specified for views, they can only be specified for tables.

You can specify multiple AFTER triggers for each triggering action

(INSERT, UPDATE, or DELETE). If you have multiple AFTER triggers for a

table, you can use sp_settriggerorder to define which AFTER trigger

fires first and which fires last. All other AFTER triggers besides the

first and last fire in an undefined order which you cannot control.

AFTER is the default in SQL Server 2000. You could not specify AFTER

or INSTEAD OF in SQL Server version 7.0 or earlier, all triggers in

those versions operated as AFTER triggers.

• INSTEAD OF -The trigger executes in place of the triggering action.

INSTEAD OF triggers can be specified on both tables and views. You can

define only one INSTEAD OF trigger for each triggering action (INSERT,

UPDATE, and DELETE). INSTEAD OF triggers can be used to perform



enhance integrity checks on the data values supplied in INSERT and

UPDATE statements. INSTEAD OF triggers also let you specify actions

that allow views, which would normally not support updates, to be

updatable.

An INSTEAD OF trigger can take actions such as:

• Ignoring parts of a batch.

• Not processing a part of a batch and logging the problem rows.

• Taking an alternative action if an error condition is encountered.

In SQL Server 6.5 you could define only 3 triggers per table, one for

INSERT, one for UPDATE and one for DELETE. From SQL Server 7.0

onwards, this restriction is gone, and you could create multiple

triggers per each action. But in 7.0 there's no way to control the

order in which the triggers fire. In SQL Server 2000 you could specify

which trigger fires first or fires last using sp_settriggerorder.

Triggers can't be invoked on demand. They get triggered only when an

associated action (INSERT, UPDATE, DELETE) happens on the table on

which they are defined.

Triggers are generally used to implement business rules, auditing.

Triggers can also be used to extend the referential integrity checks,

but wherever possible, use constraints for this purpose, instead of

triggers, as constraints are much faster. Till SQL Server 7.0,

triggers fire only after the data modification operation happens. So

in a way, they are called post triggers. But in SQL Server 2000 you

could create pre triggers also.



72. Difference between trigger and Stored procedure?



73. The following trigger generates an e-mail whenever a new title is

added in the pubs database:

CREATE TRIGGER reminder

ON titles

FOR INSERT

AS

EXEC master..xp_sendmail 'MaryM', 'New title, mention in the next

report to distributors.'



74. What are locks?

Microsoft® SQL Server™ 2000 uses locking to ensure transactional

integrity and database consistency. Locking prevents users from



reading data being changed by other users, and prevents multiple users

from changing the same data at the same time. If locking is not used,

data within the database may become logically incorrect, and queries

executed against that data may produce unexpected results.



75. What are the different types of locks?

SQL Server uses these resource lock modes.

Lock mode Description

Shared (S) Used for operations that do not change or update data

(read-only operations), such as a SELECT statement.

Update (U) Used on resources that can be updated. Prevents a common

form of deadlock that occurs when multiple sessions are reading,

locking, and potentially updating resources later.

Exclusive (X) Used for data-modification operations, such as INSERT,

UPDATE, or DELETE. Ensures that multiple updates cannot be made to the

same resource at the same time.

Intent Used to establish a lock hierarchy. The types of intent locks

are: intent shared (IS), intent exclusive (IX), and shared with intent

exclusive (SIX).

Schema Used when an operation dependent on the schema of a table is

executing. The types of schema locks are: schema modification (Sch-M)

and schema stability (Sch-S).

Bulk Update (BU) Used when bulk-copying data into a table and the

TABLOCK hint is specified.



76. What is a dead lock? Give a practical sample? How you can minimize

the deadlock situation? What is a deadlock and what is a live lock?

How will you go about resolving deadlocks?

Deadlock is a situation when two processes, each having a lock on one

piece of data, attempt to acquire a lock on the other's piece. Each

process would wait indefinitely for the other to release the lock,

unless one of the user processes is terminated. SQL Server detects

deadlocks and terminates one user's process.

A livelock is one, where a request for an exclusive lock is

repeatedly denied because a series of overlapping shared locks keeps

interfering. SQL Server detects the situation after four denials and



refuses further shared locks. A livelock also occurs when read

transactions monopolize a table or page, forcing a write transaction

to wait indefinitely.



77. nolock?

Locking Hints A range of table-level locking hints can be specified using the SELECT, INSERT, UPDATE, and DELETE statements to direct Microsoft® SQL Server™ 2000 to the type of locks to be used.

Table-level locking hints can be used when a finer control of the types of locks acquired on an object is required. These locking hints

override the current transaction isolation level for the session. Note The SQL Server query optimizer automatically makes the correct

determination. It is recommended that table-level locking hints beused to change the default locking behavior only when necessary.

Disallowing a locking level can affect concurrency adversely.



Locking hint Description

HOLDLOCK Hold a shared lock until completion of the transaction instead of releasing the lock as soon as the required table, row, or

data page is no longer required. HOLDLOCK is equivalent to SERIALIZABLE.NOLOCK Do not issue shared locks and do not honor exclusive locks.When this option is in effect, it is possible to read an uncommittedtransaction or a set of pages that are rolled back in the middle of aread. Dirty reads are possible. Only applies to the SELECT statement.PAGLOCK Use page locks where a single table lock would usually be taken.READCOMMITTED Perform a scan with the same locking semantics as atransaction running at the READ COMMITTED isolation level. By default,SQL Server 2000 operates at this isolation level.READPAST Skip locked rows. This option causes a transaction to skip rows locked by other transactions that would ordinarily appear in the

result set, rather than block the transaction waiting for the other transactions to release their locks on these rows. The READPAST lock hint applies only to transactions operating at READ COMMITTED isolation and will read only past row-level locks. Applies only to theSELECT statement.READUNCOMMITTED Equivalent to NOLOCK.REPEATABLEREAD Perform a scan with the same locking semantics as atransaction running at the REPEATABLE READ isolation level.

ROWLOCK Use row-level locks instead of the coarser-grained page- and



table-level locks.

SERIALIZABLE Perform a scan with the same locking semantics as a

transaction running at the SERIALIZABLE isolation level. Equivalent to

HOLDLOCK.

TABLOCK Use a table lock instead of the finer-grained row- or

page-level locks. SQL Server holds this lock until the end of the

statement. However, if you also specify HOLDLOCK, the lock is held

until the end of the transaction.

TABLOCKX Use an exclusive lock on a table. This lock prevents others

from reading or updating the table and is held until the end of the

statement or transaction.

UPDLOCK Use update locks instead of shared locks while reading a

table, and hold locks until the end of the statement or transaction.

UPDLOCK has the advantage of allowing you to read data (without

blocking other readers) and update it later with the assurance that

the data has not changed since you last read it.

XLOCK Use an exclusive lock that will be held until the end of the

transaction on all data processed by the statement. This lock can be

specified with either PAGLOCK or TABLOCK, in which case the exclusive

lock applies to the appropriate level of granularity.



78. For example, if the transaction isolation level is set to

SERIALIZABLE, and the table-level locking hint NOLOCK is used with the

SELECT statement, key-range locks typically used to maintain

serializable transactions are not taken.

USE pubs

GO

SET TRANSACTION ISOLATION LEVEL SERIALIZABLE

GO

BEGIN TRANSACTION

SELECT au_lname FROM authors WITH (NOLOCK)

GO



79. What is escalation of locks?

Lock escalation is the process of converting a lot of low level locks



(like row locks, page locks) into higher level locks (like table

locks). Every lock is a memory structure too many locks would mean,

more memory being occupied by locks. To prevent this from happening,

SQL Server escalates the many fine-grain locks to fewer coarse-grain

locks. Lock escalation threshold was definable in SQL Server 6.5, but

from SQL Server 7.0 onwards it's dynamically managed by SQL Server.

FAQ on Transaction in SQL Server



84. What is Transaction?

A transaction is a sequence of operations performed as a single

logical unit of work. A logical unit of work must exhibit four

properties, called the ACID (Atomicity, Consistency, Isolation, and

Durability) properties, to qualify as a transaction:

• Atomicity - A transaction must be an atomic unit of work; either all

of its data modifications are performed or none of them is performed.

• Consistency - When completed, a transaction must leave all data in a

consistent state. In a relational database, all rules must be applied

to the transaction's modifications to maintain all data integrity. All

internal data structures, such as B-tree indexes or doubly-linked

lists, must be correct at the end of the transaction.

• Isolation - Modifications made by concurrent transactions must be

isolated from the modifications made by any other concurrent

transactions. A transaction either sees data in the state it was in

before another concurrent transaction modified it, or it sees the data

after the second transaction has completed, but it does not see an

intermediate state. This is referred to as serializability because it

results in the ability to reload the starting data and replay a series

of transactions to end up with the data in the same state it was in

after the original transactions were performed.

• Durability - After a transaction has completed, its effects are

permanently in place in the system. The modifications persist even in

the event of a system failure.



85. After one Begin Transaction a truncate statement and a RollBack

statements are there. Will it be rollbacked? Since the truncate

statement does not perform logged operation how does it RollBack?

It will rollback.

**



86. Given a SQL like

Begin Tran

Select @@Rowcount

Begin Tran

Select @@Rowcount

Begin Tran

Select @@Rowcount

Commit Tran

Select @@Rowcount

RollBack

Select @@Rowcount

RollBack

Select @@Rowcount

What is the value of @@Rowcount at each stmt levels?

Ans : 0 – zero.

@@ROWCOUNT - Returns the number of rows affected by the last statement.

@@TRANCOUNT - Returns the number of active transactions for the

current connection.

Each Begin Tran will add count, each commit will reduce count and ONE

rollback will make it 0.

SQL Server FAQ on Random Category



87. What are the constraints for Table Constraints define rules

regarding the values allowed in columns and are the standard mechanism

for enforcing integrity. SQL Server 2000 supports five classes of

constraints.

NOT NULL

CHECK

UNIQUE

PRIMARY KEY

FOREIGN KEY



88. There are 50 columns in a table. Write a query to get first 25 columns

Ans: Need to mention each column names.



89. How to list all the tables in a particular database?

USE pubs

GO

sp_help



90. What are cursors? Explain different types of cursors. What are the

disadvantages of cursors? How can you avoid cursors?

Cursors allow row-by-row processing of the result sets.

Types of cursors: Static, Dynamic, Forward-only, Keyset-driven.

Disadvantages of cursors: Each time you fetch a row from the cursor,

it results in a network roundtrip, where as a normal SELECT query

makes only one roundtrip, however large the result set is. Cursors are

also costly because they require more resources and temporary storage

(results in more IO operations). Further, there are restrictions on

the SELECT statements that can be used with some types of cursors.



Most of the times, set based operations can be used instead of

cursors. Here is an example:

If you have to give a flat hike to your employees using the following

criteria:

Salary between 30000 and 40000 -- 5000 hike

Salary between 40000 and 55000 -- 7000 hike

Salary between 55000 and 65000 -- 9000 hike

In this situation many developers tend to use a cursor, determine each

employee's salary and update his salary according to the above

formula. But the same can be achieved by multiple update statements or

can be combined in a single UPDATE statement as shown below:

UPDATE tbl_emp SET salary =

CASE WHEN salary BETWEEN 30000 AND 40000 THEN salary + 5000

WHEN salary BETWEEN 40000 AND 55000 THEN salary + 7000

WHEN salary BETWEEN 55000 AND 65000 THEN salary + 10000

END

Another situation in which developers tend to use cursors: You need to

call a stored procedure when a column in a particular row meets

certain condition. You don't have to use cursors for this. This can be

achieved using WHILE loop, as long as there is a unique key to

identify each row. For examples of using WHILE loop for row by row

processing, check out the 'My code library' section of my site or

search for WHILE.



91. Dynamic Cursors?

Suppose, I have a dynamic cursor attached to table in a database. I

have another means by which I will modify the table. What do you

think will the values in the cursor be?

Dynamic cursors reflect all changes made to the rows in their result

set when scrolling through the cursor. The data values, order, and

membership of the rows in the result set can change on each fetch. All

UPDATE, INSERT, and DELETE statements made by all users are visible

through the cursor. Updates are visible immediately if they are made

through the cursor using either an API function such as SQLSetPos or

the Transact-SQL WHERE CURRENT OF clause. Updates made outside the

cursor are not visible until they are committed, unless the cursor



transaction isolation level is set to read uncommitted.



92. What is DATEPART?

Returns an integer representing the specified datepart of the

specified date.



93. Difference between Delete and Truncate?

TRUNCATE TABLE is functionally identical to DELETE statement with no

WHERE clause: both remove all rows in the table.

(1) But TRUNCATE TABLE is faster and uses fewer system and transaction

log resources than DELETE. The DELETE statement removes rows one at a

time and records an entry in the transaction log for each deleted row.

TRUNCATE TABLE removes the data by deallocating the data pages used to

store the table's data, and only the page deallocations are recorded

in the transaction log.

(2) Because TRUNCATE TABLE is not logged, it cannot activate a trigger.

(3) The counter used by an identity for new rows is reset to the seed

for the column. If you want to retain the identity counter, use DELETE

instead.

Of course, TRUNCATE TABLE can be rolled back.



94. Given a scenario where two operations, Delete Stmt and Truncate

Stmt, where the Delete Statement was successful and the truncate stmt

was failed. – Can u judge why?



95. What are global variables? Tell me some of them?

Transact-SQL global variables are a form of function and are now

referred to as functions.

ABS - Returns the absolute, positive value of the given numeric

expression.

SUM

AVG

AND



96. What is DDL?

Data definition language (DDL) statements are SQL statements that

support the definition or declaration of database objects (for

example, CREATE TABLE, DROP TABLE, and ALTER TABLE).

You can use the ADO Command object to issue DDL statements. To

differentiate DDL statements from a table or stored procedure name,

set the CommandType property of the Command object to adCmdText.

Because executing DDL queries with this method does not generate any

recordsets, there is no need for a Recordset object.



97. What is DML?



Data Manipulation Language (DML), which is used to select, insert,

update, and delete data in the objects defined using DDL



98. What are keys in RDBMS? What is a primary key/ foreign key?

There are two kinds of keys.

A primary key is a set of columns from a table that are guaranteed to

have unique values for each row of that table.

Foreign keys are attributes of one table that have matching values in

a primary key in another table, allowing for relationships between

tables.



99. What is the difference between Primary Key and Unique Key?

Both primary key and unique key enforce uniqueness of the column on

which they are defined. But by default primary key creates a clustered

index on the column, where are unique creates a nonclustered index by

default. Another major difference is that, primary key doesn't allow

NULLs, but unique key allows one NULL only.



100. Define candidate key, alternate key, composite key?

A candidate key is one that can identify each row of a table uniquely.

Generally a candidate key becomes the primary key of the table. If the

table has more than one candidate key, one of them will become the

primary key, and the rest are called alternate keys.

A key formed by combining at least two or more columns is called

composite key.



101. What is the Referential Integrity?

Referential integrity refers to the consistency that must be

maintained between primary and foreign keys, i.e. every foreign key

value must have a corresponding primary key value.



102. What are defaults? Is there a column to which a default can't be

bound?

A default is a value that will be used by a column, if no value is

supplied to that column while inserting data. IDENTITY columns and

timestamp columns can't have defaults bound to them.



103. What is Query optimization? How is tuning a performance of query

done?



104. What is the use of trace utility?



105. What is the use of shell commands? xp_cmdshell



Executes a given command string as an operating-system command shell

and returns any output as rows of text. Grants nonadministrative users

permissions to execute xp_cmdshell.



106. What is use of shrink database?

Microsoft® SQL Server 2000 allows each file within a database to be

shrunk to remove unused pages. Both data and transaction log files can

be shrunk.



107. If the performance of the query suddenly decreased where you will

check?



108. What is execution plan?



109. What is a pass-through query?

Microsoft® SQL Server 2000 sends pass-through queries as

un-interpreted query strings to an OLE DB data source. The query must

be in a syntax the OLE DB data source will accept. A Transact-SQL

statement uses the results from a pass-through query as though it is a

regular table reference.

This example uses a pass-through query to retrieve a result set from a

Microsoft Access version of the Northwind sample database.

SELECT *

FROM OpenRowset('Microsoft.Jet.OLEDB.4.0',

'c:\northwind.mdb';'admin'; '',

'SELECT CustomerID, CompanyName

FROM Customers

WHERE Region = ''WA'' ')



110. How do you differentiate Local and Global Temporary table?

You can create local and global temporary tables. Local temporary

tables are visible only in the current session; global temporary

tables are visible to all sessions. Prefix local temporary table names

with single number sign (#table_name), and prefix global temporary

table names with a double number sign (##table_name). SQL statements

reference the temporary table using the value specified for table_name

in the CREATE TABLE statement:

CREATE TABLE #MyTempTable (cola INT PRIMARY KEY)

INSERT INTO #MyTempTable VALUES (1)



111. How the Exists keyword works in SQL Server?

USE pubs

SELECT au_lname, au_fname

FROM authors

WHERE exists

(SELECT *

FROM publishers

WHERE

authors.city = publishers.city)

When a subquery is introduced with the keyword EXISTS, it functions as

an existence test. The WHERE clause of the outer query tests for the

existence of rows returned by the subquery. The subquery does not

actually produce any data; it returns a value of TRUE or FALSE.



112. ANY?

USE pubs

SELECT au_lname, au_fname

FROM authors

WHERE city = ANY

(SELECT city

FROM publishers)



113. to select date part only

SELECT CONVERT(char(10),GetDate(),101)

--to select time part only

SELECT right(GetDate(),7)



114. How can I send a message to user from the SQL Server?

You can use the xp_cmdshell extended stored procedure to run net send

command. This is the example to send the 'Hello' message to JOHN:

EXEC master..xp_cmdshell "net send JOHN 'Hello'"

To get net send message on the Windows 9x machines, you should run the

WinPopup utility. You can place WinPopup in the Startup group under

Program Files.



115. What is normalization? Explain different levels of normalization?

Explain Third normalization form with an example?

The process of refining tables, keys, columns, and relationships to

create an efficient database is called normalization. This should

eliminates unnecessary duplication and provides a rapid search path to

all necessary information.

Some of the benefits of normalization are:

• Data integrity (because there is no redundant, neglected data)

• Optimized queries (because normalized tables produce rapid,

efficient joins)

• Faster index creation and sorting (because the tables have fewer

columns)

• Faster UPDATE performance (because there are fewer indexes per table)

• Improved concurrency resolution (because table locks will affect

less data)

• Eliminate redundancy

There are a few rules for database normalization. Each rule is called

a "normal form." If the first rule is observed, the database is said



to be in "first normal form." If the first three rules are observed,

the database is considered to be in "third normal form." Although

other levels of normalization are possible, third normal form is

considered the highest level necessary for most applications.

First Normal Form (1NF)

• Eliminate repeating groups in individual tables

• Create a separate table for each set of related data.

• Identify each set of related data with a primary key.

Do not use multiple fields in a single table to store similar data.

For example, to track an inventory item that may come from two

possible sources, an inventory record may contain fields for Vendor

Code 1 and Vendor Code 2. But what happens when you add a third

vendor? Adding a field is not the answer; it requires program and

table modifications and does not smoothly accommodate a dynamic number

of vendors. Instead, place all vendor information in a separate table

called Vendors, then link inventory to vendors with an item number

key, or vendors to inventory with a vendor code key.

Another Example

Subordinate1 Subordinate2 Subordinate3 Subordinate4

Bob Jim Mary Beth

Mary Mike Jason Carol Mark

Jim Alan

Eliminate duplicative columns from the same table. Clearly, the

Subordinate1-Subordinate4 columns are duplicative. What happens when

we need to add or remove a subordinate?

Subordinate

Bob Jim

Bob Mary

Bob Beth

Mary Mike

Mary Jason

Mary Carol

Mary Mark

Jim Alan

Second Normal Form (2NF)

• Create separate tables for sets of values that apply to multiple

records.

• Relate these tables with a foreign key.

Records should not depend on anything other than a table's primary key

(a compound key, if necessary).

For example, consider a customer's address in an accounting system.

The address is needed by the Customers table, but also by the Orders,



Shipping, Invoices, Accounts Receivable, and Collections tables.

Instead of storing the customer's address as a separate entry in each

of these tables, store it in one place, either in the Customers table

or in a separate Addresses table.

Another Example:

CustNum FirstName LastName Address City State ZIP

1 John Doe 12 Main Street Sea Cliff NY 11579

2 Alan Johnson 82 Evergreen Tr Sea Cliff NY 11579

A brief look at this table reveals a small amount of redundant data.

We're storing the "Sea Cliff, NY 11579" and "Miami, FL 33157" entries

twice each. Additionally, if the ZIP code for Sea Cliff were to

change, we'd need to make that change in many places throughout the

database. Our new table (let's call it ZIPs) might look like this:

ZIP City State

11579 Sea Cliff NY

33157 Miami FL

46637 South Bend IN

Third Normal Form (3NF)

• Eliminate fields that do not depend on the key.

Values in a record that are not part of that record's key do not

belong in the table. In general, any time the contents of a group of

fields may apply to more than a single record in the table, consider

placing those fields in a separate table.

For example, in an Employee Recruitment table, a candidate's

university name and address may be included. But you need a complete

list of universities for group mailings. If university information is

stored in the Candidates table, there is no way to list universities

with no current candidates. Create a separate Universities table and

link it to the Candidates table with a university code key.

Another Example :

Order Number Customer Number Unit Price Quantity Total

1 241 $10 2 $20

2 842 $9 20 $180

The total can be derived by multiplying the unit price by the

quantity, therefore it's not fully dependent upon the primary key. We

must remove it from the table to comply with the third normal form:

Order Number Customer Number Unit Price Quantity



1 241 $10 2

2 842 $9 20

http://databases.about.com/library/weekly/aa091601a.htm

Domain/key normal form (DKNF). A key uniquely identifies each row in a

table. A domain is the set of permissible values for an attribute. By

enforcing key and domain restrictions, the database is assured of

being freed from modification anomalies. DKNF is the normalization

level that most designers aim to achieve.

**

Remember, these normalization guidelines are cumulative. For a

database to be in 2NF, it must first fulfill all the criteria of a 1NF

database.



116. If a database is normalized by 3 NF then how many number of

tables it should contain in minimum? How many minimum if 2NF and 1 NF?



117. What is denormalization and when would you go for it?

As the name indicates, denormalization is the reverse process of

normalization. It's the controlled introduction of redundancy in to

the database design. It helps improve the query performance as the

number of joins could be reduced.



118. How can I randomly sort query results?

To randomly order rows, or to return x number of randomly chosen rows,

you can use the RAND function inside the SELECT statement. But the

RAND function is resolved only once for the entire query, so every row

will get same value. You can use an ORDER BY clause to sort the rows

by the result from the NEWID function, as the following code shows:

SELECT *

FROM Northwind..Orders

ORDER BY NEWID()



119. sp_who

Provides information about current Microsoft® SQL Server™ users and

processes. The information returned can be filtered to return only

those processes that are not idle.



120. Have you worked on Dynamic SQL? How will You handled " (Double

Quotes) in Dynamic SQL?



121. How to find dependents of a table?

Verify dependencies with sp_depends before dropping an object





122. What is the difference between a CONSTRAINT AND RULE?

Rules are a backward-compatibility feature that perform some of the

same functions as CHECK constraints. CHECK constraints are the

preferred, standard way to restrict the values in a column. CHECK

constraints are also more concise than rules; there can only be one

rule applied to a column, but multiple CHECK constraints can be

applied. CHECK constraints are specified as part of the CREATE TABLE

statement, while rules are created as separate objects and then bound

to the column.



123. How to call a COM dll from SQL Server 2000?

sp_OACreate - Creates an instance of the OLE object on an instance of

Microsoft® SQL Server

Syntax

sp_OACreate progid, clsid,

objecttoken OUTPUT

[ , context ]

context - Specifies the execution context in which the newly created

OLE object runs. If specified, this value must be one of the following:

1 = In-process (.dll) OLE server only

4 = Local (.exe) OLE server only

5 = Both in-process and local OLE server allowed

Examples

A. Use Prog ID - This example creates a SQL-DMO SQLServer object by

using its ProgID.

DECLARE @object int

DECLARE @hr int

DECLARE @src varchar(255), @desc varchar(255)

EXEC @hr = sp_OACreate 'SQLDMO.SQLServer', @object OUT

IF @hr <> 0

BEGIN

EXEC sp_OAGetErrorInfo @object, @src OUT, @desc OUT

SELECT hr=convert(varbinary(4),@hr), Source=@src, Description=@desc

RETURN

END

B. Use CLSID - This example creates a SQL-DMO SQLServer object by

using its CLSID.

DECLARE @object int

DECLARE @hr int

DECLARE @src varchar(255), @desc varchar(255)

EXEC @hr = sp_OACreate '{00026BA1-0000-0000-C000-000000000046}',

@object OUT

IF @hr <> 0

BEGIN

EXEC sp_OAGetErrorInfo @object, @src OUT, @desc OUT

SELECT hr=convert(varbinary(4),@hr), Source=@src, Description=@desc

RETURN

END



124. Difference between sysusers and syslogins?



sysusers - Contains one row for each Microsoft® Windows user, Windows

group, Microsoft SQL Server™ user, or SQL Server role in the database.

syslogins - Contains one row for each login account.



125. What is the row size in SQL Server 2000?

8060 bytes.



126. How will you find structure of table, all tables/views in one db,

all dbs?

sp_helpdb - will give list of all databases

sp_helpdb pubs - will give details about database pubs. .mdf, .ldf

file locations, size of database.

select * from information_schema.tables where table_type='base table'

OR

SELECT * FROM sysobjects WHERE type = 'U' - lists all tables under

current database

***



127. What is English query?



128. B-tree indexes or doubly-linked lists?



129. What is the system function to get the current user's user id?

USER_ID(). Also check out other system functions like USER_NAME(),

SYSTEM_USER, SESSION_USER, CURRENT_USER, USER, SUSER_SID(), HOST_NAME().



130. What are the series of steps that happen on execution of a query

in a Query Analyzer?

1) Syntax checking 2) Parsing 3) Execution plan



131. Which event (Check constraints, Foreign Key, Rule, trigger,

Primary key check) will be performed last for integrity check?

Identity Insert Check

Nullability constraint

Data type check

Instead of trigger

Primary key

Check constraint

Foreign key

DML Execution (update statements)

After Trigger

**



132. How will you show many to many relation in sql?

Create 3rd table with 2 columns which having one to many relation to

these tables.

SQL Server FAQ on Random Category



87. What are the constraints for Table Constraints define rules

regarding the values allowed in columns and are the standard mechanism

for enforcing integrity. SQL Server 2000 supports five classes of

constraints.

NOT NULL

CHECK

UNIQUE

PRIMARY KEY

FOREIGN KEY



88. There are 50 columns in a table. Write a query to get first 25 columns

Ans: Need to mention each column names.



89. How to list all the tables in a particular database?

USE pubs

GO

sp_help



90. What are cursors? Explain different types of cursors. What are the

disadvantages of cursors? How can you avoid cursors?

Cursors allow row-by-row processing of the result sets.

Types of cursors: Static, Dynamic, Forward-only, Keyset-driven.

Disadvantages of cursors: Each time you fetch a row from the cursor,

it results in a network roundtrip, where as a normal SELECT query

makes only one roundtrip, however large the result set is. Cursors are

also costly because they require more resources and temporary storage

(results in more IO operations). Further, there are restrictions on

the SELECT statements that can be used with some types of cursors.



Most of the times, set based operations can be used instead of

cursors. Here is an example:

If you have to give a flat hike to your employees using the following

criteria:

Salary between 30000 and 40000 -- 5000 hike

Salary between 40000 and 55000 -- 7000 hike

Salary between 55000 and 65000 -- 9000 hike

In this situation many developers tend to use a cursor, determine each

employee's salary and update his salary according to the above

formula. But the same can be achieved by multiple update statements or

can be combined in a single UPDATE statement as shown below:

UPDATE tbl_emp SET salary =

CASE WHEN salary BETWEEN 30000 AND 40000 THEN salary + 5000

WHEN salary BETWEEN 40000 AND 55000 THEN salary + 7000

WHEN salary BETWEEN 55000 AND 65000 THEN salary + 10000

END

Another situation in which developers tend to use cursors: You need to

call a stored procedure when a column in a particular row meets

certain condition. You don't have to use cursors for this. This can be

achieved using WHILE loop, as long as there is a unique key to

identify each row. For examples of using WHILE loop for row by row

processing, check out the 'My code library' section of my site or

search for WHILE.



91. Dynamic Cursors?

Suppose, I have a dynamic cursor attached to table in a database. I

have another means by which I will modify the table. What do you

think will the values in the cursor be?

Dynamic cursors reflect all changes made to the rows in their result

set when scrolling through the cursor. The data values, order, and

membership of the rows in the result set can change on each fetch. All

UPDATE, INSERT, and DELETE statements made by all users are visible

through the cursor. Updates are visible immediately if they are made

through the cursor using either an API function such as SQLSetPos or

the Transact-SQL WHERE CURRENT OF clause. Updates made outside the

cursor are not visible until they are committed, unless the cursor



transaction isolation level is set to read uncommitted.



92. What is DATEPART?

Returns an integer representing the specified datepart of the

specified date.



93. Difference between Delete and Truncate?

TRUNCATE TABLE is functionally identical to DELETE statement with no

WHERE clause: both remove all rows in the table.

(1) But TRUNCATE TABLE is faster and uses fewer system and transaction

log resources than DELETE. The DELETE statement removes rows one at a

time and records an entry in the transaction log for each deleted row.

TRUNCATE TABLE removes the data by deallocating the data pages used to

store the table's data, and only the page deallocations are recorded

in the transaction log.

(2) Because TRUNCATE TABLE is not logged, it cannot activate a trigger.

(3) The counter used by an identity for new rows is reset to the seed

for the column. If you want to retain the identity counter, use DELETE

instead.

Of course, TRUNCATE TABLE can be rolled back.



94. Given a scenario where two operations, Delete Stmt and Truncate

Stmt, where the Delete Statement was successful and the truncate stmt

was failed. – Can u judge why?



95. What are global variables? Tell me some of them?

Transact-SQL global variables are a form of function and are now

referred to as functions.

ABS - Returns the absolute, positive value of the given numeric

expression.

SUM

AVG

AND



96. What is DDL?

Data definition language (DDL) statements are SQL statements that

support the definition or declaration of database objects (for

example, CREATE TABLE, DROP TABLE, and ALTER TABLE).

You can use the ADO Command object to issue DDL statements. To

differentiate DDL statements from a table or stored procedure name,

set the CommandType property of the Command object to adCmdText.

Because executing DDL queries with this method does not generate any

recordsets, there is no need for a Recordset object.



97. What is DML?



Data Manipulation Language (DML), which is used to select, insert,

update, and delete data in the objects defined using DDL



98. What are keys in RDBMS? What is a primary key/ foreign key?

There are two kinds of keys.

A primary key is a set of columns from a table that are guaranteed to

have unique values for each row of that table.

Foreign keys are attributes of one table that have matching values in

a primary key in another table, allowing for relationships between

tables.



99. What is the difference between Primary Key and Unique Key?

Both primary key and unique key enforce uniqueness of the column on

which they are defined. But by default primary key creates a clustered

index on the column, where are unique creates a nonclustered index by

default. Another major difference is that, primary key doesn't allow

NULLs, but unique key allows one NULL only.



100. Define candidate key, alternate key, composite key?

A candidate key is one that can identify each row of a table uniquely.

Generally a candidate key becomes the primary key of the table. If the

table has more than one candidate key, one of them will become the

primary key, and the rest are called alternate keys.

A key formed by combining at least two or more columns is called

composite key.



101. What is the Referential Integrity?

Referential integrity refers to the consistency that must be

maintained between primary and foreign keys, i.e. every foreign key

value must have a corresponding primary key value.



102. What are defaults? Is there a column to which a default can't be

bound?

A default is a value that will be used by a column, if no value is

supplied to that column while inserting data. IDENTITY columns and

timestamp columns can't have defaults bound to them.



103. What is Query optimization? How is tuning a performance of query done?



104. What is the use of trace utility?



105. What is the use of shell commands? xp_cmdshell



Executes a given command string as an operating-system command shell

and returns any output as rows of text. Grants nonadministrative users

permissions to execute xp_cmdshell.



106. What is use of shrink database?

Microsoft® SQL Server 2000 allows each file within a database to be

shrunk to remove unused pages. Both data and transaction log files can

be shrunk.



107. If the performance of the query suddenly decreased where you will

check?



108. What is execution plan?



109. What is a pass-through query?

Microsoft® SQL Server 2000 sends pass-through queries as

un-interpreted query strings to an OLE DB data source. The query must

be in a syntax the OLE DB data source will accept. A Transact-SQL

statement uses the results from a pass-through query as though it is a

regular table reference.

This example uses a pass-through query to retrieve a result set from a

Microsoft Access version of the Northwind sample database.

SELECT *

FROM OpenRowset('Microsoft.Jet.OLEDB.4.0',

'c:\northwind.mdb';'admin'; '',

'SELECT CustomerID, CompanyName

FROM Customers

WHERE Region = ''WA'' ')



110. How do you differentiate Local and Global Temporary table?

You can create local and global temporary tables. Local temporary

tables are visible only in the current session; global temporary

tables are visible to all sessions. Prefix local temporary table names

with single number sign (#table_name), and prefix global temporary

table names with a double number sign (##table_name). SQL statements

reference the temporary table using the value specified for table_name

in the CREATE TABLE statement:

CREATE TABLE #MyTempTable (cola INT PRIMARY KEY)

INSERT INTO #MyTempTable VALUES (1)



111. How the Exists keyword works in SQL Server?

USE pubs

SELECT au_lname, au_fname

FROM authors

WHERE exists

(SELECT *

FROM publishers

WHERE

authors.city = publishers.city)

When a subquery is introduced with the keyword EXISTS, it functions as

an existence test. The WHERE clause of the outer query tests for the

existence of rows returned by the subquery. The subquery does not

actually produce any data; it returns a value of TRUE or FALSE.



112. ANY?

USE pubs

SELECT au_lname, au_fname

FROM authors

WHERE city = ANY

(SELECT city

FROM publishers)



113. to select date part only

SELECT CONVERT(char(10),GetDate(),101)

--to select time part only

SELECT right(GetDate(),7)



114. How can I send a message to user from the SQL Server?

You can use the xp_cmdshell extended stored procedure to run net send

command. This is the example to send the 'Hello' message to JOHN:

EXEC master..xp_cmdshell "net send JOHN 'Hello'"

To get net send message on the Windows 9x machines, you should run the

WinPopup utility. You can place WinPopup in the Startup group under

Program Files.



115. What is normalization? Explain different levels of normalization?

Explain Third normalization form with an example?

The process of refining tables, keys, columns, and relationships to

create an efficient database is called normalization. This should

eliminates unnecessary duplication and provides a rapid search path to

all necessary information.

Some of the benefits of normalization are:

• Data integrity (because there is no redundant, neglected data)

• Optimized queries (because normalized tables produce rapid,

efficient joins)

• Faster index creation and sorting (because the tables have fewer

columns)

• Faster UPDATE performance (because there are fewer indexes per table)

• Improved concurrency resolution (because table locks will affect

less data)

• Eliminate redundancy

There are a few rules for database normalization. Each rule is called

a "normal form." If the first rule is observed, the database is said



to be in "first normal form." If the first three rules are observed,

the database is considered to be in "third normal form." Although

other levels of normalization are possible, third normal form is

considered the highest level necessary for most applications.

First Normal Form (1NF)

• Eliminate repeating groups in individual tables

• Create a separate table for each set of related data.

• Identify each set of related data with a primary key.

Do not use multiple fields in a single table to store similar data.

For example, to track an inventory item that may come from two

possible sources, an inventory record may contain fields for Vendor

Code 1 and Vendor Code 2. But what happens when you add a third

vendor? Adding a field is not the answer; it requires program and

table modifications and does not smoothly accommodate a dynamic number

of vendors. Instead, place all vendor information in a separate table

called Vendors, then link inventory to vendors with an item number

key, or vendors to inventory with a vendor code key.

Another Example

Subordinate1 Subordinate2 Subordinate3 Subordinate4

Bob Jim Mary Beth

Mary Mike Jason Carol Mark

Jim Alan

Eliminate duplicative columns from the same table. Clearly, the

Subordinate1-Subordinate4 columns are duplicative. What happens when

we need to add or remove a subordinate?

Subordinate

Bob Jim

Bob Mary

Bob Beth

Mary Mike

Mary Jason

Mary Carol

Mary Mark

Jim Alan

Second Normal Form (2NF)

• Create separate tables for sets of values that apply to multiple

records.

• Relate these tables with a foreign key.

Records should not depend on anything other than a table's primary key

(a compound key, if necessary).

For example, consider a customer's address in an accounting system.

The address is needed by the Customers table, but also by the Orders,



Shipping, Invoices, Accounts Receivable, and Collections tables.

Instead of storing the customer's address as a separate entry in each

of these tables, store it in one place, either in the Customers table

or in a separate Addresses table.

Another Example:

CustNum FirstName LastName Address City State ZIP

1 John Doe 12 Main Street Sea Cliff NY 11579

2 Alan Johnson 82 Evergreen Tr Sea Cliff NY 11579

A brief look at this table reveals a small amount of redundant data.

We're storing the "Sea Cliff, NY 11579" and "Miami, FL 33157" entries

twice each. Additionally, if the ZIP code for Sea Cliff were to

change, we'd need to make that change in many places throughout the

database. Our new table (let's call it ZIPs) might look like this:

ZIP City State

11579 Sea Cliff NY

33157 Miami FL

46637 South Bend IN

Third Normal Form (3NF)

• Eliminate fields that do not depend on the key.

Values in a record that are not part of that record's key do not

belong in the table. In general, any time the contents of a group of

fields may apply to more than a single record in the table, consider

placing those fields in a separate table.

For example, in an Employee Recruitment table, a candidate's

university name and address may be included. But you need a complete

list of universities for group mailings. If university information is

stored in the Candidates table, there is no way to list universities

with no current candidates. Create a separate Universities table and

link it to the Candidates table with a university code key.

Another Example :

Order Number Customer Number Unit Price Quantity Total

1 241 $10 2 $20

2 842 $9 20 $180

The total can be derived by multiplying the unit price by the

quantity, therefore it's not fully dependent upon the primary key. We

must remove it from the table to comply with the third normal form:

Order Number Customer Number Unit Price Quantity



1 241 $10 2

2 842 $9 20

http://databases.about.com/library/weekly/aa091601a.htm

Domain/key normal form (DKNF). A key uniquely identifies each row in a

table. A domain is the set of permissible values for an attribute. By

enforcing key and domain restrictions, the database is assured of

being freed from modification anomalies. DKNF is the normalization

level that most designers aim to achieve.

**

Remember, these normalization guidelines are cumulative. For a

database to be in 2NF, it must first fulfill all the criteria of a 1NF

database.



116. If a database is normalized by 3 NF then how many number of

tables it should contain in minimum? How many minimum if 2NF and 1 NF?



117. What is denormalization and when would you go for it?

As the name indicates, denormalization is the reverse process of

normalization. It's the controlled introduction of redundancy in to

the database design. It helps improve the query performance as the

number of joins could be reduced.



118. How can I randomly sort query results?

To randomly order rows, or to return x number of randomly chosen rows,

you can use the RAND function inside the SELECT statement. But the

RAND function is resolved only once for the entire query, so every row

will get same value. You can use an ORDER BY clause to sort the rows

by the result from the NEWID function, as the following code shows:

SELECT *

FROM Northwind..Orders

ORDER BY NEWID()



119. sp_who

Provides information about current Microsoft® SQL Server™ users and

processes. The information returned can be filtered to return only

those processes that are not idle.



120. Have you worked on Dynamic SQL? How will You handled " (Double

Quotes) in Dynamic SQL?



121. How to find dependents of a table?

Verify dependencies with sp_depends before dropping an object





122. What is the difference between a CONSTRAINT AND RULE?

Rules are a backward-compatibility feature that perform some of the

same functions as CHECK constraints. CHECK constraints are the

preferred, standard way to restrict the values in a column. CHECK

constraints are also more concise than rules; there can only be one

rule applied to a column, but multiple CHECK constraints can be

applied. CHECK constraints are specified as part of the CREATE TABLE

statement, while rules are created as separate objects and then bound

to the column.



123. How to call a COM dll from SQL Server 2000?

sp_OACreate - Creates an instance of the OLE object on an instance of

Microsoft® SQL Server

Syntax

sp_OACreate progid, clsid,

objecttoken OUTPUT

[ , context ]

context - Specifies the execution context in which the newly created

OLE object runs. If specified, this value must be one of the following:

1 = In-process (.dll) OLE server only

4 = Local (.exe) OLE server only

5 = Both in-process and local OLE server allowed

Examples

A. Use Prog ID - This example creates a SQL-DMO SQLServer object by

using its ProgID.

DECLARE @object int

DECLARE @hr int

DECLARE @src varchar(255), @desc varchar(255)

EXEC @hr = sp_OACreate 'SQLDMO.SQLServer', @object OUT

IF @hr <> 0

BEGIN

EXEC sp_OAGetErrorInfo @object, @src OUT, @desc OUT

SELECT hr=convert(varbinary(4),@hr), Source=@src, Description=@desc

RETURN

END

B. Use CLSID - This example creates a SQL-DMO SQLServer object by

using its CLSID.

DECLARE @object int

DECLARE @hr int

DECLARE @src varchar(255), @desc varchar(255)

EXEC @hr = sp_OACreate '{00026BA1-0000-0000-C000-000000000046}',

@object OUT

IF @hr <> 0

BEGIN

EXEC sp_OAGetErrorInfo @object, @src OUT, @desc OUT

SELECT hr=convert(varbinary(4),@hr), Source=@src, Description=@desc

RETURN

END



124. Difference between sysusers and syslogins?



sysusers - Contains one row for each Microsoft® Windows user, Windows

group, Microsoft SQL Server™ user, or SQL Server role in the database.

syslogins - Contains one row for each login account.



125. What is the row size in SQL Server 2000?

8060 bytes.



126. How will you find structure of table, all tables/views in one db,

all dbs?

sp_helpdb - will give list of all databases

sp_helpdb pubs - will give details about database pubs. .mdf, .ldf

file locations, size of database.

select * from information_schema.tables where table_type='base table'

OR

SELECT * FROM sysobjects WHERE type = 'U' - lists all tables under

current database

***



127. What is English query?



128. B-tree indexes or doubly-linked lists?



129. What is the system function to get the current user's user id?

USER_ID(). Also check out other system functions like USER_NAME(),

SYSTEM_USER, SESSION_USER, CURRENT_USER, USER, SUSER_SID(), HOST_NAME().



130. What are the series of steps that happen on execution of a query

in a Query Analyzer?

1) Syntax checking 2) Parsing 3) Execution plan



131. Which event (Check constraints, Foreign Key, Rule, trigger,

Primary key check) will be performed last for integrity check?

Identity Insert Check

Nullability constraint

Data type check

Instead of trigger

Primary key

Check constraint

Foreign key

DML Execution (update statements)

After Trigger

**



132. How will you show many to many relation in sql?

Create 3rd table with 2 columns which having one to many relation to

these tables.

FAQ on Administration in SQL Server

159. Explain the architecture of SQL Server?

**

160. Different types of Backups?

o A full database backup is a full copy of the database.

o A transaction log backup copies only the transaction log.

o A differential backup copies only the database pages modified after

the last full database backup.

o A file or filegroup restore allows the recovery of just the portion

of a database that was on the failed disk.

161. What are `jobs' in SQL Server? How do we create one? What is tasks?

Using SQL Server Agent jobs, you can automate administrative tasks and

run them on a recurring basis.

**

162. What is database replication? What are the different types of

replication you can set up in SQL Server? How are they used?

Replication is the process of copying/moving data between databases on

the same or different servers. SQL Server supports the following types

of replication scenarios:

Snapshot replication

Transactional replication (with immediate updating subscribers, with

queued updating subscribers)

Merge replication

163. What are the different types of replications available in

sqlserver and brief about each?

**

164. What is snapshot replication how is it different from

Transactional replication?

Snapshot replication distributes data exactly as it appears at a

specific moment in time and does not monitor for updates to the data.

Snapshot replication is best used as a method for replicating data



that changes infrequently or where the most up-to-date values (low

latency) are not a requirement. When synchronization occurs, the

entire snapshot is generated and sent to Subscribers.

Snapshot replication would be preferable over transactional

replication when data changes are substantial but infrequent. For

example, if a sales organization maintains a product price list and

the prices are all updated at the same time once or twice each year,

replicating the entire snapshot of data after it has changed is

recommended. Creating new snapshots nightly is also an option if you

are publishing relatively small tables that are updated only at the

Publisher.

Snapshot replication is often used when needing to browse data such as

price lists, online catalogs, or data for decision support, where the

most current data is not essential and the data is used as read-only.

These Subscribers can be disconnected if they are not updating the data.

Snapshot replication is helpful when:

• Data is mostly static and does not change often. When it does

change, it makes more sense to publish an entirely new copy to

Subscribers.

• It is acceptable to have copies of data that are out of date for a

period of time.

• Replicating small volumes of data in which an entire refresh of the

data is reasonable.

Snapshot replication is mostly appropriate when you need to distribute

a read-only copy of data, but it also provides the option to update

data at the Subscriber. When Subscribers only read data, transactional

consistency is maintained between the Publisher and Subscribers. When

Subscribers to a snapshot publication must update data, transactional

consistency can be maintained between the Publisher and Subscriber

because the dat
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