SQL query to find record with ID not in another table

Question

I have two tables with binding primary key in database and I desire to find a disjoint set between them. For example,

• Table1 has columns (ID

Answer 1

Fast Alternative

I ran some tests (on postgres 9.5) using two tables with ~2M rows each. This query below performed at least 5* better than the other queries proposed:

-- Count
SELECT count(*) FROM (
    (SELECT id FROM table1) EXCEPT (SELECT id FROM table2)
) t1_not_in_t2;

-- Get full row
SELECT table1.* FROM (
    (SELECT id FROM table1) EXCEPT (SELECT id FROM table2)
) t1_not_in_t2 JOIN table1 ON t1_not_in_t2.id=table1.id;