and { only { filter_eq { all_rows ; commanding officer ; n/a } } ; eq { hop { filter_eq { all_rows ; commanding officer ; n/a } ; parent unit } ; jagdgeschwader 54 } } = true
select the rows whose commanding officer record fuzzily matches to na . there is only one such row in the table . the parent unit record of this unqiue row is jagdgeschwader 54 .