DELIMITER //
DROP PROCEDURE IF EXISTS `validateUser` //

CREATE PROCEDURE validateUser(IN inUsername VARCHAR(50), IN inPassword VARCHAR(50))
BEGIN
  DECLARE outId INT;
  DECLARE outLastLoginDate DATETIME;
  SELECT outId = id, outLastLoginDate = lastLoginDate FROM users WHERE username = inUsername AND password = inPassword LIMIT 1;

  IF outId IS NOT NULL THEN
    BEGIN
      UPDATE users
      SET lastLoginDate = NOW()
      WHERE id = outId
    END;
  ELSE
    BEGIN
      SELECT -1 --Invalid username/password combination
    END;
  END IF;
END//
DELIMITER ;