Get all the rows referencing (via foreign keys) a particular row in a table

Question

This seems so simple, but I haven\'t been able to find an answer to this question.

What do I want? A master table with rows that delete themselves w

Answer 1

SELECT * 
FROM master ma
WHERE EXISTS (
    SELECT *
    FROM other ot
    WHERE ot.master_id = ma.id
    );

Or, the other way round:

SELECT * 
FROM other ot
WHERE EXISTS (
    SELECT *    
    FROM master ma
    WHERE ot.master_id = ma.id
    );

SO if you want to update (or delete) only the rows in master that are not referenced by other, you could:

UPDATE master ma
SET id = 1000+id
  , name = 'blue'
WHERE name = 'green'
AND NOT EXISTS (
    SELECT *
    FROM other ot
    WHERE ot.master_id = ma.id
    );