I keep getting this error when I tried to execute this query, although I couldn't figure out what went wrong. I'm using Oracle and JDBC.

Here's the query:

SELECT Temp.flight_number, Temp.avgprice 
FROM (SELECT P.flight_number, AVG (P.amount) AS avgprice 
        FROM purchase P 
       GROUP BY P.flight_number) AS Temp 
WHERE Temp.avgprice = (SELECT MAX (Temp.avgprice) 
                         FROM Temp)

I'm trying to get the maximum of average price of the tickets that customers have booked, group by flight_number.