I'm doing some search, where users are choosing in dropdown some clauses. When they leave some box empty, I want query to ignore clause. I know CASE, and best I thought of is that if I pass 0 to parameter in stored procedure, it ignores that parameter, like this.
WHERE a.Country = (CASE WHEN @Country > 0 THEN @Country ELSE (something else) END)so, (something else) should be like no condition, it can be '>0' as country ids are from all >1, but I don't know how to use > and = in same CASE.
Any suggestions?
5 Answers
A few ways:
-- Do the comparison, OR'd with a check on the @Country=0 case
WHERE (a.Country = @Country OR @Country = 0)
-- compare the Country field to itself
WHERE a.Country = CASE WHEN @Country > 0 THEN @Country ELSE a.Country ENDOr, use a dynamically generated statement and only add in the Country condition if appropriate. This should be most efficient in the sense that you only execute a query with the conditions that actually need to apply and can result in a better execution plan if supporting indices are in place. You would need to use parameterised SQL to prevent against SQL injection.
You can simplify to:
WHERE a.Country = COALESCE(NULLIF(@Country,0), a.Country);(something else) should be a.Country
if Country is nullable then make(something else) be a.Country OR a.Country is NULL
.. ELSE a.Country ...I suppose
Try this:
WHERE a.Country = (CASE WHEN @Country > 0 THEN @Country ELSE a.Country END)
