Returns an integer between 1 and 7 that represents the day of the week, where 1 is Monday and 7 is Sunday. The argument must be a date, a timestamp, or a valid character string representation of a date or timestamp.
Example:
Using the EMPLOYEE table, Return the day of the week that Christine Haas (EMPNO='000010') started (HIREDATE).
SELECT DAYOFWEEK_ISO(HIREDATE) FROM EMPLOYEE WHERE EMPNO = '000010'
Returns 5, which represents Friday.