Můžete použít union adn s .. having count(*)> 1 vložit null jinak vložit umístění
insert into SummaryTbl (Name,Location,Date,TicketRevenue,SnackRevenue,BeverageRevenue)
select Name, NULL,Date,sum(TicketRevenue),sum(SnackRevenue), sum(BeverageRevenue)
from MovieTheaterTbl
group by Name
HAVING COUNT(*) >1
and count(location) >1
UNION
select Name, Location,Date,sum(TicketRevenue),sum(SnackRevenue), sum(BeverageRevenue)
from MovieTheaterTbl
group by Name
HAVING COUNT(*) =1
AND count(location) = 1