what's wrong with this if/then stored proc? - mysql

Question

I'm fuzzy on when I need you use # to reference vars in mySQL. I'm coming from MS SQL where you always use it, but apparently that's not correct in mySQL.
So the below stored procedure is always executing the first IF block, even if the session value is expired - in that it's always executing the update statement. Apparently the only debug tool I could find for mySQL stored procs runs on Windows and Linux. I'm on a Mac. Wamp wamp wamp.
So yeah. Can anyone see what's wrong here? Thanks!
DELIMITER $$
CREATE DEFINER=`xxx`#`localhost` PROCEDURE `validate_session`(uid INT, token VARCHAR(256))
BEGIN
DECLARE sessId INT DEFAULT NULL;
SELECT sessId = id FROM UserSessions
WHERE userId = uid
AND sessionToken = token
AND expires > INTERVAL 2 MINUTE + NOW() ORDER BY expires DESC LIMIT 1;
IF sessId IS NOT NULL THEN
UPDATE UserSessions
SET expires = INTERVAL 2 HOUR + NOW()
WHERE id = sessId;
ELSE
DELETE FROM UserSessions
WHERE userId = uid
AND sessionToken = token;
SET #sessId = 0;
END IF;
SELECT sessId;
END
For the record what it's supposed to do in pseudo code:
if we have a session for this user, with a matching token which has not expired {
update the expiration time to 2 hours from now
return the session id;
}
else {
delete the (now stale) session
return 0;
}
Thanks in advance.

Answer 1

You're not setting the value of sessId... you're making a comparisson in your query.
I think what you need is something like this:
CREATE DEFINER=`xxx`#`localhost` PROCEDURE `validate_session`(uid INT, token VARCHAR(256))
BEGIN
DECLARE sessId INT DEFAULT NULL;
SELECT id
INTO sessId -- Here is the assignment
FROM UserSessions
WHERE userId = uid
AND sessionToken = token
AND expires > INTERVAL 2 MINUTE + NOW()
ORDER BY expires DESC
LIMIT 1;
IF sessId IS NOT NULL THEN
UPDATE UserSessions
SET expires = INTERVAL 2 HOUR + NOW()
WHERE id = sessId;
ELSE
DELETE FROM UserSessions
WHERE userId = uid
AND sessionToken = token;
SET sessId = 0;
END IF;
SELECT sessId;
END
Reference:
MySQL Reference: SELECT ... INTO syntax
MySQL Reference: Local variable scope and resolution