Get only somme attributes from DB

tj · **Posted:** Thu Aug 11, 2005 10:19 am

Hi,
is it possible to get only somme attributes of an object from Database, instead of all attributes ?
I tested ISession.CreateSQLQuery() with version 0.8.4, but it does'nt work.

thank you
tj

KPixel · **Posted:** Thu Aug 11, 2005 1:39 pm

If you are talking about lazy property fetching
read the topic Graph subset fetching

k-dub · **Joined:** Thu May 12, 2005 8:45 am **Posts:** 226

Do you perhaps mean something like this?

Code:

select user.FirstName, user.LastName from my.app.User as user

This would only return the FirstName and LastName properties of the User object, in an object array.

tj · **Posted:** Fri Aug 19, 2005 4:56 am

I thought that it is possible to get an Object instantiated by NHibernate that contains only the requested attributes.

thank you
tj

tinomen · **Joined:** Tue May 24, 2005 12:55 pm **Posts:** 56

To the best of my knowledge, it is not possible to populate a subset of properties on a mapped object using the base NHibernate framework. HQL with a SELECT statement will return an object array of the SELECT items values, even if they are all from the same object. (as was previously stated)

If you have a lot of need for this, you may want to look at integrating the iBATIS framework http://ibatis.apache.org/index.html into your DAL. Anyway you look at it it's gonna require a bit of work.

k-dub · **Joined:** Thu May 12, 2005 8:45 am **Posts:** 226

See http://nhibernate.sourceforge.net/forum/viewtopic.php?t=604 about dynamic instantiation.

Basically, you need to do this:
1. Create an object where the constructor takes the types you want to select.
2. Import it in your mappings
3. Use the "select new SubsetObject( foo.A, foo.B ) from BigObject foo where ...." syntax. See this for a better explanation.