know the day from timestamp..

See:

http://www.postgresql.org/idocs/index.php?functions-datetime.html#FUNCTIONS-DATETIME-EXTRACT

in particular for your example:

SELECT EXTRACT(DOW FROM TIMESTAMP '2002-09-12 20:44:21');

Lee.

jerome writes:
> is there a function that will say the day (monday... sunday) in numeric...
>
> input -- 2002-09-12 20:44:21+08 or just date -- 2002-09-12
>
> will output thursday or 4 just like the date command for the shell..