WHERE clause converting INT to DATETIME
To join all rows that "equal" each other:




WHERE "DA-A"."DeliveryHour"
    = '0:0'::time + "RT-A"."DeliveryHour" * interval '1h'


Or

WHERE EXTRACT(hour FROM "DA-A"."DeliveryHour")::numeric
    = "RT-A"."DeliveryHour"


One or the other may be favorable to keep one side sargable when you want to use an index in a query on one or the other side.


For the case where you are only interested in  2 / 2:00:00, your explicit expressions may be the best choice, since both expressions are sargable.