How to join using NHibernate QueryOver

Question

I have the following situation in my code and am not able to solve it. Situation -

var grpA = Session.QueryOver(() => _employeeGroupRelation));
var grpB = Session.QueryOver(() => _employeeGroup));

// var grpC should join grpA and grpB on _employeeGroupRelation.groupID = _employeeGroup.ID

Question - Is there some way to join grpA and grpB using QueryOver syntax? Is it possible to do this without using the List() on grpA or grpB, because each of them will hold close to 10,000 records and I don't want to dump them into memory. Is this the right use of QueryOver? Are there cleaner ways of achieving what I'm trying to solve?

It maybe a basic doubt, but I'm a newbie to NHib and QueryOver.

Edit -

select * from employeeGroup a
inner join employeeGroupRelation b on a.ID = b.ID

This is what I'm trying to do in SQL.

It may be more beneficial for you to ask what you are trying to achieve in SQL. I'm not sure what you are trying to do by the above. — Cole W
– Cole W, Commented Mar 27, 2012 at 20:15

Anton · Accepted Answer · 2013-06-17 13:13:06Z

10

The easiest way to do it:

session.QueryOver<EmployeeGroup>()
   .JoinQueryOver(employeeGroup => employeeGroup.EmployeeGroupRelation)
   .Take(1000) // The same as top in SQL, if you don't want load all of entities
   .TransformUsing(Transformers.DistinctRootEntity)
   .List();

"JoinQueryOver" gets "EmployeeGroup" and related "EmployeeGroupRelation" as proxy (depends from mapping) for LazyLoad

If you don't want to use LazyLoad, you can do this:

session.QueryOver<EmployeeGroup>()
   .Fetch(employeeGroup => employeeGroup.EmployeeGroupRelation).Eager
   .Take(1000) // The same as top in SQL, if you don't want load all of entities
   .TransformUsing(Transformers.DistinctRootEntity)
   .List();

"Fetch" gets "EmployeeGroup" and related "EmployeeGroupRelation" (not proxy)

edited Jun 17, 2013 at 13:13

answered Mar 27, 2012 at 21:01

Anton

1,58312 silver badges18 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Baz1nga Over a year ago

What is employeeGroup?? You have not created the alias and this will fail

Collectives™ on Stack Overflow

How to join using NHibernate QueryOver

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related