The SQL Profiler is built into the database server and can be dynamically enabled/disabled via the MySQL client utility. To begin profiling one or more SQL queries, simply issue the following command:

Two things happen once you issue this command. First, any query you issue from this point on will be traced by the server with various performance diagnostics being created and attached to each distinct query. Second, a memory table named profiling is created in the INFORMATION_SCHEMA database for your particular session (not viewable by any other MySQL session) that stores all the SQL diagnostic results. This table remains persistent until you disconnect from MySQL at which point it is destroyed.

You can read more here: Using the New MySQL Query Profiler