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From: Rob Sargent <[email protected]>
To: David G. Johnston <[email protected]>
To: [email protected] <[email protected]>
Cc: JORGE MALDONADO <[email protected]>
Subject: Re: One parent record with 3 possible child records
Date: Thu, 2 May 2024 07:37:14 -0600
Message-ID: <[email protected]> (raw)
In-Reply-To: <CAKFQuwYPeiXTT0GTrN3o7Ja7P9G9Z-LerHsdbzCDqe=SRhffyg@mail.gmail.com>
References: <CAAY=A79usb2Lbr9nUyzxyRNWLQNc-w3oTBbtUGyC2a4E-qaX3A@mail.gmail.com>
	<CAKFQuwYPeiXTT0GTrN3o7Ja7P9G9Z-LerHsdbzCDqe=SRhffyg@mail.gmail.com>



> On May 1, 2024, at 5:24 PM, David G. Johnston <[email protected]> wrote:
> 
> On Wednesday, May 1, 2024, JORGE MALDONADO <[email protected] <mailto:[email protected]>> wrote:
> 
> Let's say that tableMain has a string field called "type" with the following possible values: "residential", "industrial" and "energy". 
> 
> This, and have the same column in the other tables, but add a check constraint ensuring only the correct enum value can be specified.  Then your foreign key from the child tables to main is both the ID and the type field.
>  
> David J.
Presuming the id is unique in parent and child, what’s the value of the type field in the foreign key?  Are you saying the PK on tableMain is (type,id), perhaps for clustering purposes?

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