I got reverse-db to work on windows to SQL Server and I created the tables there with the foreign keys et al, then reversed the sucker to see what the result was.
On Thursday, Feb 13, 2003, at 13:58 US/Eastern, Matthew Baird wrote:
now I'm confused.
let's recap:
- objects are related based on foreign keys, right?
- you can load objects in ojb based on any value, either in PB or in odmg, so a select myclass where myclass.somerelatedobject.someattribute=? will work. OJB will generate the appropriate joins for you. queries can be run without inflating a proxy, since it is, at the end of the day, just a sql query.
"For example, if A refers to a B, then in order to make the query "Give me
all the As where B's name is X, do I have to really have all those B's
instantiated within the A's? I dont want to have to retrieve all those B's
from the database unless I actually want the B's."
psuedo-oql
select A.B where A.B.name='X' will return all the B's and if the reference to A is unidirectional from A, or marked lazy, then all the A's will only be materialized when you access them.
-----Original Message-----
From: David Mitchell [mailto:[EMAIL PROTECTED]]
Sent: Thursday, February 13, 2003 10:43 AM
To: 'OJB Users List'
Subject: RE: foreign keys... last time I swear :)
Ok, I guess I pretty much understand it. You use the reference name to do a
lookup on the referenced object. So if I want to join two tables on
something other than a primary key, I need to use a hand-written sql query.
Im okay with that.
I believe I will also have to use hand-written sql for my other joins,
because I cannot use either lazy-materialization for those foreign objects,
nor prefetch that object. I only want to be able to query by those fields
without ever actually obtaining the foreign object.
For example, if A refers to a B, then in order to make the query "Give me
all the As where B's name is X, do I have to really have all those B's
instantiated within the A's? I dont want to have to retrieve all those B's
from the database unless I actually want the B's.
In other words, I cant say "select A.* from A, B where a.b.name='XXX'",
unless I have already retrieved the B from the database, to know what it's
name is.
To answer myself, unless someone corrects my misunderstanding, I have to
still write my own SQL query. This is again just fine with me, as long as I
know it's the only way to do it.
-dave
-----Original Message-----
From: Matthew Baird [mailto:[EMAIL PROTECTED]]
Sent: Thursday, February 13, 2003 12:26 PM
To: OJB Users List
Subject: RE: foreign keys... again
the docs may not be clear, but the examples are pretty clear.
...
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