Mysql stored procedure cant get the id of the object - mysql

Question

CREATE DEFINER=`root`#`localhost` PROCEDURE `add_card`(author VARCHAR(50),newtext VARCHAR(600),title VARCHAR(200),newSource VARCHAR(2300), username VARCHAR(50), tags VARCHAR(600))
BEGIN
DECLARE strLen INT DEFAULT 0;
DECLARE SubStrLen INT DEFAULT 0;
DECLARE cardId INT DEFAULT 0;
DECLARE tagId INT DEFAULT 0;
DECLARE tempTagId INT DEFAULT -1;
DECLARE temp VARCHAR(200);
INSERT INTO cards (author,text,title,username,source) VALUES (author,newtext,title,username,newSource);
SET #cardId = LAST_INSERT_ID();
Select #cardId;
IF tags IS NULL THEN
SET tags = '';
END IF;
do_this:
LOOP
SET strLen = CHAR_LENGTH(tags);
SET #temp = SUBSTRING_INDEX(tags, ',', 1);
SELECT tagId INTO tempTagId FROM tag WHERE tagName = #temp limit 1;
Select tempTagId;
SELECT tagId FROM tag WHERE tagName = 'ss';
IF tempTagId = -1 THEN
INSERT INTO tag (tagName) VALUES (#temp);
SET #tagId = LAST_INSERT_ID();
select #tagId+10;
IF NOT EXISTS (SELECT * FROM cards_tags WHERE tagId = #tagId AND cardId = #cardId) THEN
INSERT INTO cards_tags (tagId,cardId) VALUES (#tagId,#cardId);
Select #cardId;
END IF;
ELSE
IF NOT EXISTS (SELECT * FROM cards_tags WHERE tagId = tempTagId AND cardId = #cardId) THEN
INSERT INTO cards_tags (tagId,cardId) VALUES (tempTagId,#cardId);
select #tagId;
END IF;
END IF;
SET SubStrLen = CHAR_LENGTH(SUBSTRING_INDEX(tags, ',', 1)) + 2;
SET tags = MID(tags, SubStrLen, strLen);
IF tags = '' THEN
LEAVE do_this;
END IF;
END LOOP do_this;
END
It is the damnest thing i have ever seen i guess. I have this stored procedure and in the line
SELECT tagId FROM tag WHERE tagName = 'ss';
I am trying to get the id of the object but it is returning 0.
created another stored procedure
CREATE DEFINER=`root`#`localhost` PROCEDURE `adds_card`()
BEGIN
DECLARE temp VARCHAR(200);
SET #temp ='ss';
SELECT tagId FROM tag WHERE tagName = #temp;
END
And this returns 3 which is true. Why is the first one returning 0? Driving me really crazy. Spent 5 hours on it and couldnt solve it.

Answer 1

One line in your code is:
SELECT tagId INTO tempTagId FROM tag WHERE tagName = #temp limit 1;
#temp is not defined anywhere, although temp is. So, #temp defaults to NULL (or to the previous session value) and the WHERE clause likely fails.
I strongly recommend prepending local variables with a prefix, so they are not confused with column names. So I would recommend:
SELECT tagId INTO v_tempTagIdFROM tag WHERE tagName = v_temp limit 1;
or:
SELECT v_tempTagIdFROM := tagId
FROM tag
WHERE tagName = v_temp
LIMIT 1;