Equivalent to VB AndAlso in SQL?

Question

Is there an equivalent to VB's AndAlso/OrElse and C#'s &&/|| in SQL (SQL Server 2005). I am running a select query similar to the following:

SELECT a,b,c,d
FROM table1
WHERE 
(@a IS NULL OR a = @a)
AND (@b IS NULL OR b = @b)
AND (@c IS NULL OR c = @c)
AND (@d IS NULL OR d = @d)

For example, if the "@a" parameter passed in as NULL there is no point in evaluating the 2nd part of the WHERE clause (a = @a). Is there a way to avoid this either by using special syntax or rewriting the query?

Thanks, James.

Answer 1

The query engine will take care of this for you. Your query, as written, is fine. All operators will "short circuit" if they can.

Answer 2

Try this:

AND a = ISNULL(@a,a)

This function looks at @a. If it is not null it equates the expression

AND a = @a

If it is null it equates the expression

AND a = a

(Since this is always true, it replaces the @b is null statement)

Answer 3

The only way to guarantee the order of evaluation is to use CASE

WHERE
   CASE
      WHEN @a IS NULL THEN 1
      WHEN a = @a THEN 0
      ELSE 0
   END = 1
   AND /*repeat*/

In my experience this is usually slower then just letting the DB engine sort it out.

TerrorAustralis's answer is usually the best option for non-nullable columns