Re: One parent record with 3 possible child records

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От Rob Sargent
Тема Re: One parent record with 3 possible child records
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Msg-id CCFD24A0-A331-4633-AC9A-714F7F18B5DF@gmail.com
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Ответ на Re: One parent record with 3 possible child records  ("David G. Johnston" <david.g.johnston@gmail.com>)
Ответы Re: One parent record with 3 possible child records
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On May 1, 2024, at 5:24 PM, David G. Johnston <david.g.johnston@gmail.com> wrote:

On Wednesday, May 1, 2024, JORGE MALDONADO <jorgemal1960@gmail.com> 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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