Du kan prova nästa fråga:
select SS.sightseeingId, SS.SightseeingName, SS.displayPrice, MAX(SST.fromDate)
from tblSightseeings SS inner join
tblSightseeingTours SST on SS.sightseeingId = SST.sightseeingId
where SS.isActive = 1 and SS.isDisplayOnMainPage = 1
GROUP by SS.sightseeingId, SS.SightseeingName, SS.displayPrice