unsigned long
mysql_thread_id(MYSQL *mysql)
          Returns the thread ID of the current connection. This value
          can be used as an argument to
          mysql_kill() to kill the
          thread.
        
          If the connection is lost and you reconnect with
          mysql_ping(), the thread ID
          changes. This means you should not get the thread ID and store
          it for later. You should get it when you need it.
        
            This function does not work correctly if thread IDs become
            larger than 32 bits, which can occur on some systems. To
            avoid problems with
            mysql_thread_id(), do not
            use it. To get the connection ID, execute a SELECT
            CONNECTION_ID() query and retrieve the result.