It should be '='

select * from ChildTable where not exists (select 1 from ParentTable where ChildTable.fielda = ParentTable.fielda) 

>Thank you very much.
>
>>select * from ChildTable where not exists (select 1 from ParentTable where ChildTable.fielda != ParentTable.fielda)
>>
>>>I must be missing something very simple. I am trying to find records in the child table that have no corresponding records in the parent table. Here is what I do:
>>>
>>>

>>>select * from ChildTable join ParentTable where ChildTable.fielda != ParentTable.fielda
>>>

>>>
>>>But it does not work. TIA.