How to delete rows using an outer join

Question

I\'ve got a problem to delete records from a PostgreSQL table, using a LEFT JOIN.

I\'d like to delete rows I get with the following query:

S         


        

Answer 1

Good work, sun. Minor suggestion: when using EXISTS/NOT EXISTS you don't need to SELECT *. A common convention (docs) is to just write SELECT 1 as like this:

DELETE FROM url WHERE NOT EXISTS (
  SELECT 1 FROM link_type WHERE url.link_type = link_type.id 
);

Functionally, both ways work.

Answer 2

Still don't understand why my previous query doesn't work (if someone could explain, would be nice), but here is how I did the trick:

DELETE FROM url WHERE NOT EXISTS (SELECT * FROM link_type WHERE url.link_type = link_type.id );