Question

I have a database with many tables.. and each table has stored only IDs. Now what I want to do is:

SELECT id FROM table1, table2, table3
GROUP BY id;

but I also want to sort them by decreasing order of occurrence.

For example the IDs that are in all 3 tables should appear on top and the IDs appearing in only one table should be at the bottom. Any clue on how to do this?

Answer 1

Try this too

select id from
(
    SELECT id FROM table1
    union all
    select id from table2
    union all
    select id from table3 
) as t
GROUP BY id
order by count(id) desc