My table has three columns
ID parent_ID item
As you can understand, it's for a nested menu. Now I need to find those elements which don't have any child elements. In other words, whose id isn't being used as parent_ID for any other rows( and order them by item
). Can I do this with a mysql query?
SELECT * FROM mytable m WHERE NOT EXISTS (SELECT 1 FROM mytable m2 WHERE m2.parent_ID = m.ID)
I would use a LEFT JOIN instead of a subquery:
SELECT Parents.* FROM mytable Parents
LEFT JOIN mytable Childs ON Parents.ID = Childs.parent_ID
WHERE Childs.ID IS NULL
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.