Question

I want to create a stored procedure. If the parameter is -1 then there should not be a where clause on that column else there should be a WHERE clause. What’s the best way to do it without a lot of IF branching?

I checked the archive. There are a few similar questions but not exactly the same.

CREATE PROCEDURE report
(
  @site int,
  @promo int,
  @type int
)
AS
SET NOCOUNT ON

-- I want to avoid this:
IF @site = -1 AND @promo = -1 and @type = -1
BEGIN
  SELECT * from table
END
IF @site > -1 AND @promo = -1 and @type = -1
BEGIN
  SELECT * from table WHERE site = @site;
END
... -- other cases


ELSE  -- all parameters are > -1
BEGIN
  SELECT * from table 
  WHERE site = @site AND promo = @promo AND type = @type
END

Answer 1

This works in many cases, (despite what the comments will say without trying it) because the optimiser will ignore the ISNULL bit. Only works for non-null columns

SELECT @site = NULLIF(@site, -1) ...

SELECT * from table  
  WHERE site = ISNULL(@site, site) ..

Otherwise, conditional WHERE which is usually bad because OR can not be optimised

SELECT * from table  
  WHERE (@site = -1 OR site = @site) AND  (...

Or separate stored procedures (don’t think you want that either)

Or use sp_executesql (avoids dynamic SQL)