Conditional Operator in SQL Where Clause

Question

I\'m wishing I could do something like the following in SQl Server 2005 (which I know isnt valid) for my where clause. Sometimes @teamID (passed into a stored procedure) wi

Answer 1

Even simpler than Andomar's answer, and assuming that id is never 0 (as for most auto-increment ids) is

SELECT  Team.teamID 
FROM    Team
WHERE   @teamid = 0 or Team.teamID = @teamid;

That predicate is always true when @teamid is zero, and otherwise only true when it matches a particular row's teamId.

Note however: this works pretty efficiently on Sybase 11 or above; it worked pretty inefficiently on MS SQL server 2003; I don't know how it works on the current version of MS SQL Server.

Also, you can use case; you just have to put the case in where clause, not the where clause in the case. So your original query would be:

Select Team.teamID 
From Team
where 
   case when @teamid = 0 then 0 else Team.teamID end = @teamId;

Note that this is likely to be less efficient, however, as it must be evaluated per row and will also likely result in a full table scan.

The form I gave above is more likely to be rewritten by a smart query optimizer (your mileage depends on your RDBMS) to use an index when @teamid is not zero.