updating 3 columns with a select clause

if anyone could help with this one, i'd appreciate it:

i have a table:
ncc1701-e> desc update_test

 Name                            Null?    Type
 ------------------------------- -------- ----
 DATE_STRING                              VARCHAR2(50)
 REAL_DATE                                DATE
 COUNT_DATE                               NUMBER
 TIME_WO_SYSDATE                          NUMBER

for every value of date_string i want to update real_date, count_date, time_wo_sysdate using a data function on the date_string value. ie: date_string='20000701'
i want real_date to = to_date(date_string,'YYYYMMDD') count_date to = length(date_string)
time_wo_sysdate to = (sysdate - to_date(date_string,'YYYYMMDD')

how can i do this in an update statement? i was thinking of using something like:
update update_test
set real_date = (select to_date(date_string,'YYYYMMDD') from update_test), count_date = (select length(date_string) from update_test), time_wo_sysdate = (select (sysdate - to_date(date_string, 'YYYYMMDD')) from update_test) where
date_string like '2000%'
and real_date is null;

this works if the update_test table has one row, how can i make it work for many rows? also, how can i ensure that the values returned by the select statements match the row of the update statement (how would the rowid's match)?

i know that i could do this in pl/sql with a for loop and matching the rowid's but i was wondering if i could do this as a simple update statement.

thanks alot for any help in advance.
-maurice
samuels_at_seas.upenn.edu Received on Tue Aug 01 2000 - 00:00:00 CDT