MySQL slow query log

Probably the best way to locate and diagnose troublesome MySQL queries is through utilization of MySQL's slow query log. If enabled, MySQL will log any query that takes longer than long_query_time seconds (default is 10 seconds) to run to a file. The log file by default is in the MySQL data directory and named SERVER-slow.log. For the details on how to configure and utilize the slow query log, see the MySQL documentation.