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

There is no defined evaluation order in a SQL statement -- except in the case of case expressions, and even there the order isn't so much defined as the result guaranteed. The conditions in your where clause could theoretically be done in parallel or alternating order.

Case expressions differ not by having a defined order, but by having a guaranteed result. IOW, case when 1=1 then 0 When longrunningfunction() = 1 then 2 end is guaranteed to return zero, but there is no promise not to run the longrunningfunction.