Select all rows that have no children

select yt.name
    from YourTable yt
    where not exists (select null from YourTable where parentID = yt.id)

Although less efficient (see: Left outer join vs NOT EXISTS), you could also do this with a left join:

select yt1.name
    from YourTable yt1
        left join YourTable yt2
            on yt1.id = yt2.parentID
    where yt2.id is null

select t.name
from that_table t
where t.id not in (select parentID from that_table);

Tags:

Mysql

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