Explain in sql server query

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SQL-Server-2005

The following solution is for getting 6th highest salary from Employee table ,

SELECT TOP 1 salary
FROM (
SELECT DISTINCT TOP 6 salary
FROM employee
ORDER BY salary DESC) a
ORDER BY salary

In above query what is the meaning of 'a'

Posted 16-Aug-12 0:17am

devausha

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bbirajdar · Accepted Answer · 2012-08-16T00:27:00

Solution 1

'a' stands for a alias. You can use any valid variable name instead of 'a' and the result will be the same.

The pseudo code equivalent to the above query which will help you understand.....

SQL

SELECT DISTINCT TOP 6 salary
FROM employee
ORDER BY salary DESC as  a

-- The result of above query is assigned to 'a' and then the 'a' is queried as shown below.

SELECT TOP 1 salary
FROM a
ORDER BY salary

Posted 16-Aug-12 0:27am

bbirajdar

Comments

Mehdi Gholam 16-Aug-12 6:30am

5'ed, just posted the same!

ridoy 16-Aug-12 6:39am

good explanation..

bbirajdar 16-Aug-12 7:22am

Thank you :)

Mehdi Gholam · Accepted Answer · 2012-08-16T00:29:00

Solution 2

"a" is an alias usually you would write "as a" for clarity. This is used if you need to reference inner query columns like:

SQL

select t.name from (select * from tablename) as t

Posted 16-Aug-12 0:29am

Mehdi Gholam

Comments

bbirajdar 16-Aug-12 6:34am

Yes.. correct answer.. +5

ridoy 16-Aug-12 6:40am

it's right too..

Santhosh Kumar Jayaraman · Accepted Answer · 2012-08-16T00:38:00

a its just an alias.

For the inner subquery, you are just setting an alias as a.

This is similar to how we are setting alias to table.

SQL

select * from tbl a.

here 'a' is an alias for table tbl...
Like this 'a' is an alias for the query

SQL

SELECT DISTINCT TOP 6 salary
FROM employee
ORDER BY salary DESC

You can set any name to the alias.