Question

I’m dealing with a MySQL table that defines the JobName column as UNIQUE. If somebody tries to save a new Job to the database using a JobName that is already in the database, MySQL throws a warning.

I would like to be able to detect this warning, just like an error, in my PHP script and deal with it appropriately. Ideally I would like to know what kind of warning MySQL has thrown so that I can branch the code to handle it.

Is this possible? If not, is it because MySQL doesn’t have this ability, PHP doesn’t have this ability, or both?

Answer 1

For warnings to be ‘flagged’ to PHP natively would require changes to the mysql/mysqli driver, which is obviously beyond the scope of this question. Instead you’re going to have to basically check every query you make on the database for warnings:

$warningCountResult = mysql_query('SELECT @@warning_count'); if ($warningCountResult) {     $warningCount = mysql_fetch_row($warningCountResult );     if ($warningCount[0] > 0) {         //Have warnings         $warningDetailResult = mysql_query('SHOW WARNINGS');         if ($warningDetailResult ) {             while ($warning = mysql_fetch_assoc($warningDetailResult) {                 //Process it             }         }     }//Else no warnings } 

Obviously this is going to be hideously expensive to apply en-mass, so you might need to carefully think about when and how warnings may arise (which may lead you to refactor to eliminate them).

For reference, MySQL SHOW WARNINGS

Of course, you could dispense with the initial query for the SELECT @@warning_count, which would save you a query per execution, but I included it for pedantic completeness.