EJB-QL Question

[Dale Seng]

If we had a "Boss" EJB with a single CMR field named "employee", and an Employee EJB using a "Pay" class as its pay CMP field, are both of these allowable:

SELECT b.employee FROM Boss b
SELECT b.employee.pay FROM Boss b

--Dale--
[ May 15, 2004: Message edited by: Dale Seng ]

[Dale Seng]

Here's a second question, if you please...

Say we have a one to many relationship: House 1 ---- * Room (a house is made of of several rooms, one room may belong to only one house), and House has a collection-valued relation field whose value is 'room'.

Our database looks like this:

 
House        Room
------------------------
Smith        Kitchen
Smith        LivingRoom
Jones        Kitchen
Jones        Den

Can we do this:

SELECT OBJECT(h)
FROM House h, IN(h.room) r
WHERE r = 'Kitchen'

--Dale--
[ May 15, 2004: Message edited by: Dale Seng ]

[Shahfazal Mohammed]

Hi-

I guess when you say a 1--* relationship, it's more better represented when the entities are different tables - House table and Room table (you know, normalization and stuff)
and, technically, when you say a collection-valued relation field - 'room', it's a getter method getRoom() (or more comfortably getRooms() when your cmr-field is 'rooms') which will return a Collection of local component interfaces of the Room entity bean (a different table), so that you can iterate thru them. your database might actually have to be modified as

     House                            Room
-------------------          ------------------------
HID      House_Name          RID    Room_Name     HID
-------------------          ------------------------
1        Smith               r1     Kitchen       1
2        Jones               r2     Living Room   1
                             r3     Kitchen       2
                             r4     Den           2

in this case your EJB-QL would look something like -

SELECT OBJECT(h)
FROM House h, IN(h.room) r
WHERE r.Room_Name = 'Kitchen'

hope this helps