Question

I’ve got a SQL Server 2005 database. I need to get distinct values in addition to calling a function on those distinct values. I’m not sure how the distinct works when there is a function call involved. For example, I have this query:

SELECT DISTINCT a, b, c, fcn_DoSomething(a, b, c) AS z FROM users

I’m guessing that the function (fcn_DoSomething) is being called for all of the values in the table, not the distinct values. Am I correct? If so, how can I write the query to call the function only on distinct values of a,b,c? I know one option is to use a temporary table, but if anyone has better ideas that would be great.

Thanks

Answer 1

This would ensure that the function only got called on distinct values.

select *, fcn_DoSomething(a, b, c) 
from
 (select distinct a,b,c FROM users) v

However, I believe that the function call will be optimised, so it may not make a difference. Give it a try.