debasis.yours

 Profile Answers by debasis.yours 

• Dec 14th, 2007

 

Sub-query is an inner query that returns a result used by another outer query may be by means of an IN operator like the following:
select * from [dbo].[Orders] where [Customer_ID] IN (select Customer_ID from [dbo].[Customer] where [City]='Kolkata')
A Co-query is a part of a UNION query.
A subquery can also be used with = operator; but in that case it must have to be guaranteed that it will return only one row of result