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

It depends on how SQL Server optimizes the query, you could run the Query Analyzer to see for your particular case

A sure fire way to optimize would to say

    WITH QueryResult AS (
    SELECT 
        someFields 
    FROM 
        someTable 
    WHERE 
        cheapLookup=1 
    )

SELECT * FROM QueryResult WHERE (CAST(someField as FLOAT)/otherField)<0.9