Returns a number from 1 to 7 representing the day of the week of the specified date, with Sunday=1, Monday=2, and so on.
DOW ( date-expression )
The following statement returns the value 5.
SELECT DOW( '1998-07-09' ) FROM iq_dummy
See the section “DATE_FIRST_DAY_OF_WEEK option”, if you need Monday (or another day) to be the first day of the week.