Is the SQL WHERE clause short-circuit evaluated?

Question

Are boolean expressions in SQL WHERE clauses short-circuit evaluated ?

For example:

SELECT * 
FROM Table t 
WHERE @key IS NULL OR (@key IS NOT NULL          


        

Answer 1

This takes an extra 4 seconds in query analyzer, so from what I can see IF is not even shorted...

SET @ADate = NULL

IF (@ADate IS NOT NULL)
BEGIN
    INSERT INTO #ABla VALUES (1)
        (SELECT bla from a huge view)
END

It would be nice to have a guaranteed way!