Need SQL Query to find Parent records without child records

Question

I am not at all conversant in SQL so was hoping someone could help me with a query that will find all the records in a parent table for which there are no records in a child

Answer 1

If you do a left join on the child table and simply say where the child parentID is null.

SELECT ParentTable.ParentID FROM ParentTable P
    Left Join ChildTable C on C.ParentID = P.ParentID
    WHERE C.Id IS NULL;