Re: A situation with one parent table and 3 child tables
| От | David G. Johnston |
|---|---|
| Тема | Re: A situation with one parent table and 3 child tables |
| Дата | |
| Msg-id | CAKFQuwZbmqeLoHBzuOkVjd4qXyNUi1tcuhf8bECK+2c-DGK9iw@mail.gmail.com обсуждение исходный текст |
| Ответ на | A situation with one parent table and 3 child tables (JORGE MALDONADO <jorgemal1960@gmail.com>) |
| Ответы |
Re: A situation with one parent table and 3 child tables
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| Список | pgsql-sql |
On Monday, October 2, 2023, JORGE MALDONADO <jorgemal1960@gmail.com> wrote:
Hi,I have one parent table (table_p) with 3 child tables (table_ch1, table_ch2 and table_ch3). Each record of the parent table can be associated with 1 and only 1 child table records. This means that:* Some records of the table_p will link to records of table_ch1* Some records of the table_p will link to records of table_ch2* Some records of the table_p will link to records of table_ch3At first look, this does not make very much sense to me. I thought about considering 3 parent tables, one for each child table. However, the 3 parent tables would have the same exact structure and I would like to know if there is a workaround for this issue.
You are thinking of it backwards. Your chN tables will have FK pointing back to the p table. I suggest adding some kind of type column to the p table indicating which chN table the row belongs to. Then have the same column on the chN table with a check constraint. The key is then the id and that type. You can, with a bit of effort, ensure a row exists on the chN table for every row on the p table but it is circular so must be deferred in enforcement.
David J.
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