Problems writing a linked query in SQL

[Thorben Grosser]

Hello Newsgroup,

I am doing some archive database and therefore got one table indexing
every folder and one table storing which rack belongs to which
department, eg:

table folders :
+-----------+------+-------+
| folder_id | rack | date |
+===========+======+=======+
| 123456789 | 325 | 05/02 |
+-----------+------+-------+
| 987654321 | 158 | 02/07 |
+-----------+------+-------+
| 987485221 | 666 | 01/05 |
+-----------+------+-------+

table racks:
+----+------+------------+
| id | rack | department |
+====+======+============+
| 1 | 158 | FKA/PKG |
+----+------+------------+
| 2 | 555 | KOV/GDA |
+----+------+------------+
| 3 | 666 | FKA/PKG |
+----+------+------------+
| 4 | 123 | ORG/RET |
+----+------+------------+

Now I have to select all the folders which have for example an equal
date belonging to a certain department, meaning:
- I have to find the racks belonging to eg "FKA/PGK" (158, 666)
- Then I'll got to find every folder belonging to the racks 666 and
158 (987485221, 987654321)
- Then I've got to find those which belong to a certain condition (eg.
date <02/2001)
Sure I could do that in three queries, but somehow I've got the
feeling that SQL is powerfull enough to do this in one query.
But how?

thanks in advance
Thorben Grosser