Group By OR ?

I have a query that produces the following result set:
Effect. Date Expir. Date Cert. Type
7/23/2002 7/22/2005 O
5/10/2004 7/22/2005 P
7/23/2005 7/22/2008 O
7/23/2005 7/22/2008 P
The last two lines have the exact same dates. Is there a way to rollup
the last two lines to give one line like
7/23/2005 7/22/2008 O, P
'
Mia J.
*** Sent via Developersdex http://www.examnotes.net ***You have never read a book on RDBMS, have you? WHAT IS THE DEFINITION
OF 1NF (First Normal Form)'
Please, please, please read at least one book on RDBMS before you kill
someone with your programming.