Sorry, I made a mistake with my original SQL statement, it should have been:

Select * from dbo.SystemDataDictionary union all select * from dbo.ApplicationDataDictionary order by DataID

The clause I'm matching is SystemDataDictionary.DataField and ApplicationDataDictionary.DataField, where if the record exists in SystemDataDictionary and ApplicationDataDictionary I'd like to keep the result from SystemDataDictionary. If the record appears in either, but not both, then include that in the result set too.

Regards

ps - I'll say thank you and add a gold star too this time! :-)