Path: utzoo!mnetor!uunet!lll-winken!lll-lcc!ames!elroy!cit-vax!ucla-cs!sdcrdcf!trwrb!scgvaxd!ashtate!cy
From: cy@ashtate (Cy Shuster)
Newsgroups: comp.databases
Subject: Re: Referential Integrity Constraints (Long)
Message-ID: <502@ashton.UUCP>
Date: 1 Mar 88 19:39:53 GMT
References: <1342@polyslo.UUCP>
Reply-To: cy@ashtate.UUCP (Cy Shuster)
Organization: Ashton-Tate, Glendale, CA
Lines: 13
Keywords: Referential Integrity, Triggers, SYBASE, UNIFY
Summary: CODASYL databases provide integrity without triggers

I'm surprised you had to write code for a CODASYL DBMS to enforce
cascaded deletes. In the IDMS implementation, at least, there are a
robust set of set membership options which automatically perform many
of those functions (e.g. ERASE PERMANENT on mandatory sets).

As an aside, it's interesting that while dBASE Mac is not "purely"
relational since relationships need to be predefined (even though they
are implemented through simple foreign keys), it is exactly via this
predefinition that we are able to support referential integrity. Without
full support of domains, a DBMS must still have some kind of advance 
knowledge about what constraints to support. How are integrity rules
defined in other DBMSs (save writing custom triggers)?

--Cy--     dBASE Mac Development    UUCP:...seismo!scgvaxd!ashtate!cy