-- When was it recored that a property was owned by the 
-- customer who owned at some time property 7797?
-- Valid-time nonsequenced and transaction-time nonsequenced
SELECT P2.property_number, P2.TT_Start AS Recorded_Start
FROM Prop_Owner P1, Prop_Owner P2
WHERE P1.property_number = 7797
  AND P2.property_number <> P1.property_number
  AND P1.customer_number = P2.customer_number
  AND P1.TT_Start <= P2.TT_Start AND P2.TT_Start < P1.TT_Stop;
