Delete Parent record if child is not present

Question

I am creating menu and submenus in a table variable. ( Typical parent child records in the same table) ParentID coll is null for all Top menus. And for their child ParentID

Answer 1

Without seeing your table structure it's difficult to tell you the exact query you would need but, if I understand your question correctly, you just need to do something like this:

DELETE T 
FROM MyTable T 
WHERE NOT EXISTS(SELECT * FROM MyTable WHERE ParentID = T.MenuID)
    AND T.ParentID IS NULL

This query does a correlated subquery to find all the menu records that don't have child records. It uses SQL's EXISTS clause

Answer 2

You could do something like this:

delete from yourtable yt where not exists (select * from yourtable yt2 where yt.id = yt2.parentid) and yt.parentid is null

Answer 3

A single statement like this should do it (as an alternative to using exists):

delete p
from
    tblMenu p
    left join tblMenu c on p.ID = c.ParentID
where 
    p.ParentID is null --Ensures that the item to delete is at the top
    and c.ParentID is null --Finds top level items with no children