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POCreating relations: #1452 - Cannot add or update a child row: a foreign key constraint fails
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7274494
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2011-09-01T18:03:52.493
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2011-09-01T19:43:54.437
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2011-09-01T19:43:54.437
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I've tried to create a new table relation but I seem to have gotten an error for which I'm not sure why. The first relation (one to many) I made was last week and it works good, maybe I forgot the correct procedure since then? Simple explanation: I have three tables - events, music_styles, venues So far, I correctly linked events and venues in the way that one venue can have multiple events linked to it. I tried making a new table that has rows for each musical style and an ID that would be used in table 'events' so that I can link each event to a musical style id. However this is the error I got: <blockquote> SQL query: ALTER TABLE <code>events</code> ADD FOREIGN KEY ( <code>MUSIC_STYLE_ID</code> ) REFERENCES <code>nightl7_complete</code>.<code>music_styles</code> ( <code>MUSIC_ID</code> ) ON DELETE NO ACTION ON UPDATE NO ACTION ; MySQL said: Documentation <h1>1452 - Cannot add or update a child row: a foreign key constraint</h1> fails (<code>nightl7_complete/#sql-2721_c0dcfd</code>, CONSTRAINT <code>#sql-2721_c0dcfd_ibfk_2</code> FOREIGN KEY (<code>MUSIC_STYLE_ID</code>) REFERENCES <code>music_styles</code> (<code>MUSIC_ID</code>) ON DELETE NO ACTION ON UPDATE NO ACTION) Documentation Error ALTER TABLE <code>events</code> ADD FOREIGN KEY ( <code>MUSIC_STYLE_ID</code> ) REFERENCES <code>nightl7_complete</code>.<code>music_styles</code> ( <code>MUSIC_ID</code> ) ON DELETE NO ACTION ON UPDATE NO ACTION ; </blockquote> And this is the procedure I did :) <img src="https://i.stack.imgur.com/l91iN.jpg" alt="enter image description here"> <a href="https://i.imgur.com/d5L62.jpg" rel="nofollow noreferrer">I uploaded a full sized image here</a> Thanks everyone :) <hr> Edit: So I did this: <pre><code>$query = 'SELECT e.* FROM events e '. 'LEFT JOIN nightl7_complete.music_styles ms ON ms.ID = e.MUSIC_STYLE_ID'. 'WHERE ms.id IS NULL'; $result = mysql_query($query); if (!$result) { die('Invalid query: ' . mysql_error()); } </code></pre> and got this: Invalid query: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'ms.id IS NULL' at line 1
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Creating relations: #1452 - Cannot add or update a child row: a foreign key constraint fails
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