Question

How do I select all IDs from table_x that are not present in any row of table y in column_foo ?

I’m struggling to do this with a single SQL query.

Answer 1

It’s better to avoid subqueries if you can. An INNER JOIN will return only rows that meet the join criteria.

SELECT DISTINCT
    x.id
FROM
    table_x x
    INNER JOIN table_y y ON (x.id = y.id_column_in_y)