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Is it possible to give a query in the from clause

jayaprakash r

16y3.6kSQL

Hi all,

Is it possible to give a sql query in the from clause befor the giving a table name.
for instance:-

select top 1 Salary from(select top 2 Salary from sstable order by Salary desc) aas

it is working but
my question is what is happening here

Whether a table is created virtually in the name aas

2 Replies

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Venkatesan Jayakantham16y ago
As specified by drishty, the query select top 2 Salary from sstable order by Salary desc is a derived table. It will created temporarily in the memory and the second query will be executed on the result set of the derived table.

Cheers,
Venkatesan Prabu .J
http://venkattechnicalblog.blogspot.com/
DRISHTY16y ago
Hello,
Select query in from clause is called derived table.
They are created on the fly and then use these derived tables within your query. In very basic terms, a derived table is a virtual table that's calculated on the fly from a select statement.
In concept this is similar to creating a temporary table and then using the temporary table in your query, but the approach is much simpler, because it can all be done in one step.