Re: Column Naming Question

From: --CELKO-- <71062.1056_at_compuserve.com>
Date: 6 May 2003 11:04:44 -0700
Message-ID: <c0d87ec0.0305061004.158b1425_at_posting.google.com>

>> Since these two fields [sic] will be foreign keys relating to
Users.user_id (read ISO-11179 rules for dat element names) how can I contain this data in the table - I can't have two columns called user_id in my Files table...

Think about the semantics; users are a domain, while lenders and borrowers from that domain. This is a 3-ary relationship. I have made guesses about the business rules when I wrote the constriants -- that's why we ask people to post DDL and specs.

CREATE TABLE Checkouts
(uploader_id INTEGER NOT NULL -- lender

          REFERENCES Users(user_id)
          ON UPDATE CASCADE,
 borrower_id INTEGER NOT NULL
          REFERENCES Users(user_id)
          ON UPDATE CASCADE,
 file_name VARCHAR(128) NOT NULL
         REFERENCES Files(file_name)
         ON DELETE CASCADE
         ON UPDATE CASCADE,

 PRIMARY KEY (uploader_id, borower_id, file_name)); Received on Tue May 06 2003 - 20:04:44 CEST