How to 'insert if not exists' in php MySQL : <p>I started by googling, and found this article which talks about mutex tables.</p>

<p>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)?</p>

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

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