SQL Server conditional where clause based on declared variable

Question

Is it possible to have conditional where clause, based on declared variable?

Please note: my query is much more complicated than this, I am just using this example to simplify things.

Something like:

DECLARE @ITEST INT = 1

SELECT NAME, LNAME, CADDRESS
FROM JEEVEN
WHERE
CASE WHEN @ITEST = 1 THEN
(
    (EVEN_KEY > 5 AND EVEN_KEY < 10)
)
CASE WHEN @TEST = 2 THEN
(
    (EVEN_KEY > 20 AND EVEN_KEY < 30)
) 

Answer 1

You are looking for this

DECLARE @ITEST INT = 1

SELECT NAME, LNAME, CADDRESS
FROM JEEVEN
WHERE (@ITEST = 1 AND EVEN_KEY > 5 AND EVEN_KEY < 10)
   OR (@ITEST = 2 AND EVEN_KEY > 20 AND EVEN_KEY < 30)