>>>Another thing, that with JOIN you have there you will get 6 records with the same key from parent table and if you set tstParent.prntid as keyfield you will get nothing good but "Update Conflict" :) It will work only if you set tstChild.prntid as a keyfield.
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>>I mean here that it will be good only for updating fields in tstChild table, because all fields from txtParent in the view (6 records in the view) will point to the same record in tstParent table.
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>Actually, that was the expected behavior ( same parent record )
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>I see in the View designer that I must set a field to a "KeyField" before I can set it to updateable. Does that make sense to you? It doesn't to me. What if the field I want to update is NOT a keyfield?

This is right. Without at least one key field you cannot make other fields updatable. Keyfield may be also updateable or not.