Sql Server predicates lazy?

Question

I have a query:

SELECT 
    someFields 
FROM 
    someTable 
WHERE 
    cheapLookup=1 
    AND (CAST(someField as FLOAT)/otherField)<0.9

Answer 1

What you're referring to is short-circuiting, like other languages (e.g. C#) support.

I believe SQL Server can short-circuit but depends on the scenario / what happens in the optimizer so there is certainly not a guarantee that it will. It just might.

Excellent reference on this by Remus Rusanu here:
http://rusanu.com/2009/09/13/on-sql-server-boolean-operator-short-circuit/