Question: Setup:  

One table called `documents` with columns `author_id` and `reviewer_id` (among others).  

One table called `users` with column `user_id`.

I need to create two referential integrity links:  

One-to-many between `user_id` and `author_id`.  

One-to-many between `user_id` and `reviewer_id`.

In other words, these two columns in `documents` are independent of one another, but both should have a value that is a valid `user_id`.

Adding either one of these relationships works fine. When I try to add a second relationship in the `Edit Relationships` window, Access complains with the following message:

*Microsoft Office Access can't enforce referential integrity for this relationship.*

I've searched, but couldn't find any solutions to this. Any ideas on how this relationship could be configured?

Answer: 
To add two individual relationships from one table to two different fields in another, you need to have multiple instances of the parent table in the relationship window.

So, you'd add your Users and Documents table to the relationships window and create the first relationship. Then add the Users table to the relationship window a second time (it will be aliased as Users\_1), and then add the second relationship from this aliased copy. 

This is completely consistent with the same way you'd define two such joins in the QBE, so I'd say it's not problematic at all. But it's not necessarily obvious!
First, I suggest you change you columns' names to `author_user_id` and `reviewer_user_id` respectively, to make it clear that each reference `user_id`.

Second, you should be aware that use of Access's UI tools are not compulsory. Many of us find them unintuitive but happily there are alternatives. One is to use SQL DDL e.g. [ANSI-92 Query Mode](http://office.microsoft.com/en-gb/access/HP030704831033.aspx):

```
ALTER TABLE Documents ADD 
   CONSTRAINT fk__ document_author_user_id__Users
   FOREIGN KEY (author_user_id)
   REFERENCES Users (user_id)
   ON DELETE NO ACTION
   ON UPDATE NO ACTION
;

ALTER TABLE Documents ADD 
   CONSTRAINT fk__ reviewer_user_id__Users
   FOREIGN KEY (reviewer_user_id)
   REFERENCES Users (user_id)
   ON DELETE NO ACTION
   ON UPDATE NO ACTION
;

```

Third, consider you may need a `CHECK` constraint (or Table[sic] Validation Rule) to ensure a user cannot review their own work e.g. 

```
ALTER TABLE Documents ADD 
   CONSTRAINT document_author_cannot_review_their_own_work
   CHECK (author_user_id <> reviewer_user_id)
;

```