DAYOFWEEK() — Returns the day of the week as an integer between 1 and 7.
DAYOFWEEK( timestamp-value )
The DAYOFWEEK() function returns an integer value between 1 and 7 representing the day of the week in a timestamp value. For the DAYOFTHEWEEK() function, the week starts (1) on Sunday and ends (7) on Saturday.
This function produces the same result as using the DAY_OF_WEEK keyword with the EXTRACT() function.
The following example uses DAYOFWEEK() and the DECODE() function to return a string value representing the day of the week for the specified TIMESTAMP value.
SELECT eventtime, DECODE(DAYOFWEEK(eventtime), 1, 'Sunday', 2, 'Monday', 3, 'Tuesday', 4, 'Wednesday', 5, 'Thursday', 6, 'Friday', 7, 'Saturday') AS eventday FROM event ORDER BY eventtime;