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From: Paul M. Aoki <aoki@postgres.Berkeley.EDU>
To: keen@ms.uky.edu
Cc: postgres@postgres.Berkeley.EDU
Subject: Re: 'retrieve into' in a rule?
Date: Mon, 09 May 94 16:01:46 -0700
Message-ID: <199405092301.QAA29200@faerie.CS.Berkeley.EDU> (raw)
In-Reply-To: <9405091459.aa05728@s.s.ms.uky.edu>

keen@ms.uky.edu writes:
> "define rule r5 is on 
> retrieve to emp.age where current.age ISNULL
>  do [retrieve into x (emp.all) where emp.dept= current.dept ] \g"
> but when I actually try to retrieve from emp, 
> "retrieve (emp.all) \g"
> I get a message that "type x already defined" 
> and no tuples are retrieved.

so is this rule run more than once?

you're using the tuple-level rule system, so if there is more
than one emp with null age, the rule will be fired more than
once.  of course, once the rule is fired, there's now an "x"
table and any following firings of the rule will blow out the 
whole query (because "x" already exists).

seems like you should probably append to x (if you can do so).
--
  Paul M. Aoki  |  CS Div., Dept. of EECS, UCB  |  aoki@postgres.Berkeley.EDU
                |  Berkeley, CA 94720           |  ...!uunet!ucbvax!aoki

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