Syntax:
SLEEP(duration)

Sleeps (pauses) for the number of seconds given by the duration
argument, then returns 0. If SLEEP() is interrupted, it returns 1. The
duration may have a fractional part given in microseconds. This
function was added in MySQL 5.0.12.

URL: http://dev.mysql.com/doc/refman/5.0/en/miscellaneous-functions.html

