[Hibernate] use aggregate functions

[zqzuk <ziq...@ho...>]

Hi, i wouldlike to use aggregate functions in HQL, and i got such problems
while experimenting with the query...

i have a class Booking like

Booking(id, tutor,week,package,date,fee,term,note,student,order)

i wouldl like to do a query as such : "

"SELECT DISTINCT tutor, week, COUNT(DISTINCT student) AS numOfStudents
FROM Booking WHERE term=:tm GROUP BY
tutor,week"

problem 1 is - the query does not work because i got an error telling me
that group by clause must include all variables of this Booking class, i e ,
i changed my query to

"SELECT DISTINCT tutor, week, COUNT(DISTINCT student) AS numOfStudents
FROM Booking WHERE term=:tm GROUP BY
tutor,week, id, package, date,fee,term,note,student,order"

and it works. however, it seems that the query produces a list of Booking
objects, not only the variables tutor, week, and numOfStudents as specified
in the SELECT clause. as a result i got 2nd problem

problem 2 - i actually defined another class called "Rota(tutor, week,
numOfStudents)"

and i did 
Rota t = (Rota) queryResult.get(0);

and i got a ClassCastException. i guess the reason is that the query
produces a list of Booking objects other than the only selected variables as
in the select clause; therefore i changed to
Booking b =(Booking) queryResult.get(0);

unsurprisingly it doesnt work i guess its because in the select clause i
have another variable "numOfStudnets" which is not defined in Booking.

i dont know what to do... i certainly donot want to add a variable of
"numOfStudent" to Booking class.. but i dont know any other solutions to
this problems. seems HQL makes aggregate query much more complicated, or im
doin this in totally wrong way?
all in all, all i want to do is to get the values of "tutor, week, and
numberOfStudents" from the query, nothing else.

any ideas please help! thank you.

-- 
View this message in context: http://www.nabble.com/use-aggregate-functions-tf2108930.html#a5813279
Sent from the Hibernate forum at Nabble.com.