Combining two SQL Statements

Hello,
I need to combine this two SQL-Statements to one SQL:

1. select UserId, UsedSlots from user_used_slots;

UserId       UsedSlots
  a             3
  b             5
  a             4
  c             3
  b             5

2. select UserId, FreeSlots from user_free_slots;

UserId       FreeSlots
  a             4
  b             5
  b             3
  c             3
  b             5

==> The resulting SQL-Staetement should show something like this:
(TotalSlots = UsedSlots + FreeSlots)

UserId       UsedSlots     FreeSlots     TotalSlots
   a             7             4             11
   b            10            15             25
   c             3             3              6

How can I produce a Output which calculates everything correctly?? Thanks,
Michael Received on Thu Oct 07 2004 - 03:17:05 CDT