CASE in WHERE, SQL Server

Question

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

Answer 1

You can simplify to:

WHERE a.Country = COALESCE(NULLIF(@Country,0), a.Country);

Answer 2

Try this:

WHERE a.Country = (CASE WHEN @Country > 0 THEN @Country ELSE a.Country END)

Answer 3

(something else) should be a.Country

if Country is nullable then make(something else) be a.Country OR a.Country is NULL

Answer 4

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 END

Or, 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.

Answer 5

.. ELSE a.Country ...

I suppose