How to replace in syntax when calling stored procedure?

[Clement Yap]

Hi I am not sure how to replace values in the syntax when calling the stored procedure. Please advise. Please see my codes.

Here's my created stored procedure:-

DELIMITER $$

DROP PROCEDURE IF EXISTS `dbprodigy`.`numOfTests` $$
CREATE PROCEDURE `dbprodigy`.`numOfTests` (IN yr varchar(255), IN mth varchar(255))
BEGIN
select count(distinct SN) from tester where Date > yr"-"mth"-01 00:00:00" and Date < yr"-"mth"-31 24:00:00";
END $$

DELIMITER ;

Here's my call:-

call numOfTests("2012","03");

My call returns nothing.
Clement