mysql select query

[safra]

Can't figure out an efficient way to search for the following:

My table has two columns called 'id' and 'parent'. This is used to create some sort of a tree system where parent refers to the id of the parent node.

I want to search for all rows that have no child rows attached to them. In other words, those rows for which the id is never found as a parent.

Anyone knows how to do this?

Thanks!

[bradgrafelman]

One possibility:

SELECT id, parent
FROM myTable t1
WHERE NOT EXISTS (
    SELECT TRUE
    FROM myTable t2
    WHERE t2.parent = t1.id
)