Question

It’s possible to find a table name by an id?
I have multiple tables that extends another table, when I find the id in the “super” table, I’d like to know in which subtable is that id.
There is a way with indexing to do that or another way?
Thanks

Answer 1

Your example is really unclear but …

article(stuff,id)
news(id references article(id),morestuff)
courses(id references article(id),evenmorestuff)

So you’re using the id from article to link to either news or courses and would like to avoid select union from news AND courses ?

1) your current query does not contain this information

2) A few ways to do this:

a) you change your datamodel to something more generic (article,r_article_news,news,r_article_courses,courses) and determine that on this basis

b) you add the information in the article table (add a column named type, where you will enter either news or courses)

c) you make your first query slightly heavier to determine that automatically

SELECT a.*,b.type 
FROM article a 
INNER JOIN 
    (SELECT id,'news' AS type 
    FROM news 
    UNION 
    SELECT id,'courses' AS type 
    FROM courses) b 
ON a.id=b.id;