How to say it in SQL?

Table a:
RefObjectID, RefClassID

1,1
1,2
1,3
1,4
1,5
1,6
1,7
2,1
2,8
2,9
2,10

Table b:
RefClassID, RefTableID

1,1
1,2
1,3
2,1
2,3
3,1
3,2
3,3
4,1
4,2
4,3
4,4
5,1
5,2
5,3
5,4
6,1
6,2
6,3
7,1
7,2
7,3
8,1
8,10
8,11
9,1
9,10
9,12
10,1

What i need is:
I want to know all RefTableID's from b which belong to one RefObjectID in a but only these which are the same for all RefClassID's

when a.RefObjectID=2 then the answer should be 1

when a.RefObjectID=1 then the answer should be 1 and 3

i tried in my Code a Select on table a and than a loop through the RecordSet to bulid another Statement in this form:

Select RefTableID FROM b Where RefClassID=1 Intersect
Select RefTableID FROM b Where RefClassID=8 Intersect
Select RefTableID FROM b Where RefClassID=9 Intersect
Select RefTableID FROM b Where RefClassID=10

But in the real programm the number of Classes from table a which belong to an RefObjectID are about 800-900 and you can imagine how long the String with the statement will be.

Also the trafic on the network is to high because i need the Relation Tables to Object very often.

The Summary of tables which are togeher is also to get easy but this i do not mean:

SELECT DISTINCT(RefTableID) FROM b
WHERE RefClassID IN (SELECT RefClassID FROM a WHERE RefObjectID=2) Received on Wed Nov 26 2003 - 13:43:07 CET