Message-ID: <24fd6621-db02-24a1-0808-fd11a17fe262@klingler.net>
Date: Wed, 5 Jan 2022 13:19:11 +0100
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To: pgsql-sql@lists.postgresql.org
From: Richard Klingler <richard@klingler.net>
Subject: Return product category with hierarchical info
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Good afternoon (o;


First of all, am I am totally no expert in using PGSQL but use it mainly 
for simple web applications...


Now I have a table which represents the categories for products in a 
hierarchical manner:

     id | name | parent


So a top category is represented with parent being 0:

     1 | 'Living' | 0


The next level would look:

     2 | 'Decoration' | 1


And the last level (only 3 levels):

     3 | 'Table' | 2


So far I'm using this query to get all 3rd level categories as I use the 
output for datatables editor as a product can only belong to the lowest 
category:

select id, name from category
where parent in (select id from category where parent in (select id from 
category where parent = 0))

But this has a problem as more than one 3rd level category can have the 
same name, therefore difficult to distinguish in the datatables editor 
which one is right.


So now my question (finally ;o):


Is there a simple query that would return all 3rd levels category ids 
and names together with the concatenated names of the upper levels? 
Something like:


     3 | 'Table' | 'Living - Decoration'


thanks in advance

richard


PS: If someone could recommend a good ebook or online resource for such 
stupid questions, even better (o;