title: Is MySQL's SLEEP() function a busy-wait?
body: <p>I have a user who has inserted a number of "SELECT SLEEP(2);" queries into their code, and I am trying to figure out the impact of this query on database performance. The queries show up in the MySQL slow query log, and mk-tools report the queries as taking a substantial portion of exec time, though it's not clear if that equates to actual CPU time.</p>