How to 'insert if not exists' in MySQL?

Posted by warren on Stack Overflow See other posts from Stack Overflow or by warren
Published on 2009-09-01T08:56:41Z Indexed on 2010/06/11 18:42 UTC
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php

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sql

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mysql

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Performance

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primary-key

I started by googling, and found this article which talks about mutex tables.

I have a table with ~14 million records. If I want to add more data in the same format, is there a way to ensure the record I want to insert does not already exist without using a pair of queries (ie, one query to check and one to insert is the result set is empty)?

Does a unique constraint on a field guarantee the insert will fail if it's already there?

It seems that with merely a constraint, when I issue the insert via php, the script croaks.

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