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Multitable delete with TRIGGER.

Posted on 2014-11-23
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Last Modified: 2014-11-23
Neilsr helped me get started with my first stored procedure. Here is what I have now after rewriting his example for my database. Below is an abbreviated version of a 13 table delete. When I try to import it into phpmysql I get a 1064 syntact error after BEGIN. Every table involved including gallery has a galid.

I have tried:
WHERE tags.galid = OLD.id
WHERE tags.galid = OLD.galid

Maybe the problem is else where. Can someone help? Thanks.

DELIMITER $$
DROP TRIGGER IF EXISTS gal_delete;

CREATE TRIGGER gal_delete AFTER DELETE on gallery
FOR EACH ROW
BEGIN

DELETE FROM tags
    WHERE galid = OLD.id;

DELETE FROM comments
    WHERE galid = OLD.id;

DELETE FROM log
    WHERE galid = OLD.id;

END$$

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Question by:kadin
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2 Comments
 
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Accepted Solution

by:
chaau earned 500 total points
ID: 40461313
Because you have changed the delimiter you need to use $$ after your DROP statement:
DELIMITER $$
DROP TRIGGER IF EXISTS gal_delete$$

CREATE TRIGGER gal_delete AFTER DELETE on gallery
FOR EACH ROW
BEGIN

DELETE FROM tags
    WHERE galid = OLD.id;

DELETE FROM comments
    WHERE galid = OLD.id;

DELETE FROM log
    WHERE galid = OLD.id;

END$$

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However, I cannot help but notice that in your case a FOREIGN KEY with the CASCADE DELETE option could be a better approach.    
What you can do is create the foreign keys in each of your child tables this way:
ALTER TABLE tags
    ADD FOREIGN KEY
    fk_tags_galid (galid)
    REFERENCES gallery (galid)
    ON DELETE CASCADE
    ON UPDATE CASCADE 

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(I have added ON UPDATE CASCADE, meaning that when you update the galid in the master table it will be automatically updated in the child. You can remove this clause if your business rules are different)
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Author Comment

by:kadin
ID: 40461464
That was it. Thanks for your help. I will think about your foriegn key suggestion.
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