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Asked: 2026-06-03T06:06:10+00:00

When i need to know if something in unique before it gets inserted. i

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When i need to know if something in unique before it gets inserted. i usually just attempt to insert it and then if it fails, check if the mysql_errno() is 1062. If it is i know it failed as a duplicate key and i can do whatever i need to do.

The most common place for this is in a user table. I set the email as unique as thats the “username” for logging in. Instead of running additional queries to check uniqueness when processing registration forms, i just compile the query, execute it and check for the 1062 error number. If it fails with 1062 i tell the user nicely that the email is registered and all is good.

However i recently set up a very basic MITM sql query function which gives myself and other developers on the system access to query times, a log of all the sql queries at the bottom of the page, and most importantly, a function which establishes the mysql connection to the correct database on demand (rather than having to do the connect and pass link identifiers manually).

In the sql error query log this function creates on disk, is all my duplicate entries. This obviously doesn’t look good to other people seeing errors (even though there handled and expected). Is there a way of surpressing errors somehow for this but still being able to check the mysql_errno() ?

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  1. Editorial Team

    Whilst doing a bit of housework on my account here at SO, I thought it best to answer this with my findings so i can close it. This is basically a conclusion from my last comment above.

    If you (like me) use certain error codes in mysql in your application to reduce validation queries or code (duplicate key being the most common i find). The only way to stop an error being thrown is to catch the error inside mysql and handle it. I wont go into the how-to here but a good place to get started is:

    http://dev.mysql.com/doc/refman/5.0/en/declare-handler.html

    Note: just for the new dev’s out there, also dont forget to check out “ON DUPLICATE KEY” (google it). It was something blindly suggested to me elsewhere. It doesn’t fit in this example but i’ve used it for year’s to save checking for duplicate records before insertion (it does not return a failure on duplicate entries, so its only good if you were thinking of using a duplicate error handler to instead perform an update… hence finding your way here)

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