using greatest function

Hi:
  I have to find the most recent date from 2 tables:

table cust:

CID        NOT NULL   NUMBER(8)
OPENDATE              DATE

and table site:
SID        NOT NULL   NUMBER(8)
CID        NOT NULL   REF OF CUST_t
SDATE      NOT NULL   DATE

  A cust may have 1 or more site records. I need to find the most recent OPENDATE or the most recent SDATE, which ever is more recent. For example:
CID OPENDATE SID SDATE

1141   09-MAR-2002   101    09-MAR-2002
1141   09-MAR-2002   102    11-MAR-2002
1141   09-MAR-2002   103    01-APR-2002

  Should chose 01-APR-2002, since it is the most recent of all the SDATEs and the cust's OPENDATE

  I have:
select greatest(opendate,max(sdate)) from site s,cust c where s.cid.cid=c.cid
but SQL says "not a single group-by function"   Any help is appreciated.
- Rolf. Received on Tue Apr 23 2002 - 15:49:08 CDT