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Re: 5 tables with 3 different relation cases - Mailing list pgsql-sql

From Rob Sargent
Subject Re: 5 tables with 3 different relation cases
Date
Msg-id 66d7f649-fef5-0df2-f485-7a9eb3ee832e@gmail.com
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In response to 5 tables with 3 different relation cases  (JORGE MALDONADO <jorgemal1960@gmail.com>)
Responses Re: 5 tables with 3 different relation cases  (Steve Midgley <science@misuse.org>)
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On 12/13/21 7:32 PM, JORGE MALDONADO wrote:
Hi,

I have 5 tables related among them so that:

* T1 is parent of T2 
* T2 is parent of T3
* T3 is parent of T4
* T4 is parent of T5

image.png

However, in some cases one table is missing so that:

* T1 is parent of T3 
* T3 is parent of T4
* T4 is parent of T5
image.png

3 relations in total.

And yet, in some cases an additional table is missing so that:

* T1 is parent of T4,
* T4 is parent of T5

image.png
The 5 tables always have the exact same fields but, of course, the relations are different among each case.

Is there a way to design the schema so that I always have 5 tables and make T2 and T3 "invisible" for cases #1 and #2?

Or should I consider 12 tables: 5 for case #1, 4 for case #2 and 3 for case #3.

I will very much appreciate your feedback.

Respectfully,
Jorge Maldonado
Have you rejected using a single table with exactly the same columns + parent_id?
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