How to Short-Circuit SQL Where Clause

Question

I am trying to perform the following query in SQL server:

declare @queryWord as nvarchar(20) = \'asdas\'

SELECT  * FROM TABLE_1 
WHERE (ISDATE(@queryWord) =         


        

Answer 1

SQL Server does not do short-circuiting (nor should it).

If you need it to not try something under some circumstances, you need to force that in the way that you write your query.

For this query the easiest fix would be to use a CASE expression in your WHERE clause.

declare @queryWord as nvarchar(20) = 'asdas'

SELECT  * FROM TABLE_1 
WHERE TABLE_1.INIT_DATE = (CASE WHEN ISDATE(@queryWord) = 1 
                                THEN CONVERT(Date, @queryWord)
                           ELSE NULL  END)

Off-hand, CASE and query-nesting are the only two supported ways that I can think of to force an order of evaluation for dependent conditions in SQL.