How to catch duplicate key error 1062

Hi

Does anyone know how I would catch a duplicate key error 1062, thrown by MySQL?

I’m trying to import data into the EE database automatically, upon receipt from an external source, but I obviously don’t want to import the same data twice, hence I’m adding a unique key based on the data row to be inserted.

The 1062 error is thrown before testing with

if($this-EE->db-query($sql)) { ...

I’ve tried to catch the error by using

if (mysql_errno() == 1062) {...

and setting

$db['expressionengine']['db_debug'] = FALSE;

in config/database.php, but this has no effect. I’m still getting the error being thrown before anything else.

Does anyone know how to handle this?

Thanks in advance.

~ Steve