Composite Primary Key Cascading

Question

Two fields, Building and Room, make up a unique primary composite key in my rooms table. The key validates and saves, etc.

I have a BLANK Objects table which has three fields which will make it unique (again a composite primary key). The tables are as follows:

ROOM TABLE
[Building]     [Room]
01             101A
01             102
02             101A

OBJECT TABLE
[Building]     [Room]     [Number]
01             101A       1
01             101A       2
01             102        1
02             101A       1

How do I enforce referential integrity? When editing the relationships in MS Access' relationship tool, I get the following error: No unique index found for the referenced field of the primary table. I know (by trying non-unique values) that the composite keys for the primary (Object) table is correct. What am I doing wrong? How do I set up the proper relationships and maintain integrity (as updates will be a gruelling challenge without them)?

Answer 1

You need to set up your key like so:

Note that the primary key for rooms is set to Building + Room and for Objects it is Building + Room + Numb (Number is a reserved word AFAIR)