MySQL get first and last day of week

# For current week
select curdate() - interval weekday(curdate()) day as `Monday of week`;
select curdate() + interval (6-weekday(curdate())) day as `Sunday of week`;

# For specific date: 2012-10-20
select '2012-10-20' - interval weekday('2012-10-20') day as `Monday of week`;
select '2012-10-20' + interval (6-weekday('2012-10-20')) day as `Sunday of week`;