WEEKDAY() — Returns the day of the week as an integer between 0 and 6.
WEEKDAY( timestamp-value )
The WEEKDAY() function returns an integer value between 0 and 6 representing the day of the week in a timestamp value. For the WEEKDAY() function, the week starts (0) on Monday and ends (6) on Sunday.
This function is provided for compatibility with MySQL and produces the same result as using the WEEKDAY keyword with the EXTRACT() function.
The following example uses WEEKDAY() and the DECODE() function to return a string value representing the day of the week for the specified TIMESTAMP value.
SELECT eventtime, DECODE(WEEKDAY(eventtime), 0, 'Monday', 1, 'Tuesday', 2, 'Wednesday', 3, 'Thursday', 4, 'Friday', 5, 'Saturday', 6, 'Sunday') AS eventday FROM event ORDER BY eventtime;