Using SELECT resultset to run UPDATE query with MySQL Stored Procedures - sql

Question

I'm trying to understand MySQL Stored Procedures, I want to check if a users login credentials are valid and if so, update the users online status:
-- DROP PROCEDURE IF EXISTS checkUser;
DELIMITER //
CREATE PROCEDURE checkUser(IN in_email VARCHAR(80), IN in_password VARCHAR(50))
BEGIN
SELECT id, name FROM users WHERE email = in_email AND password = in_password LIMIT 1;
-- If result is 1, UPDATE users SET online = 1 WHERE id = "result_id";
END //
DELIMITER ;
How Can I make this if-statement based on the resultsets number of rows == 1 or id IS NOT NULL?

Answer 1

DELIMITER //
CREATE PROCEDURE checkUser(IN in_email VARCHAR(80), IN in_password VARCHAR(50))
BEGIN
DECLARE tempId INT DEFAULT 0;
DECLARE tempName VARCHAR(50) DEFAULT NULL;
DECLARE done INT DEFAULT 0;
DECLARE cur CURSOR FOR
SELECT id, name FROM users WHERE email = in_email AND password = in_password;
DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;
OPEN cur;
REPEAT
FETCH cur INTO tempId, tempName;
UPDATE users SET online = 1 WHERE id = tempId;
UNTIL done = 1 END REPEAT;
CLOSE cur;
SELECT tempName;
END //
DELIMITER ;
NB: I have not tested this. It's possible that MySQL doesn't like UPDATE against a table it currently has a cursor open for.
PS: You should reconsider how you're storing passwords.
Re comment about RETURN vs. OUT vs. result set:
RETURN is used only in stored functions, not stored procedures. Stored functions are used when you want to call the routine within another SQL expression.
SELECT LCASE( checkUserFunc(?, ?) );
You can use an OUT parameter, but you have to declare a user variable first to pass as that parameter. And then you have to select that user variable to get its value anyway.
SET #outparam = null;
CALL checkUser(?, ?, #outparam);
SELECT #outparam;
When returning result sets from a stored procedure, it's easiest to use a SELECT query.

Answer 2

Use:
UPDATE USERS
SET online = 1
WHERE EXISTS(SELECT NULL
FROM USERS t
WHERE t.email = IN_EMAIL
AND t.password = IN_PASSWORD
AND t.id = id)
AND id = 'result_id'
Why do you have LIMIT 1 on your SELECT? Do you really expect an email and password to be in the db more than once?

Answer 3

You could try an if statement if you have an result which returns 1
i looked at yor code, it seems nothing returns a true so you have to refactor it,
as above omg wrote thats realy true why do you have an limit 1 in your select query where only one emailadress can exisst?
something like this
update users set if(result==1,online=1,online=0) where email=emailadress