Adding conditions to outer joins with NHibernate ICriteria/QueryOver query

问题

Is there a way to specify additional conditions on outer joins in NHibernate when querying using QueryOver or ICriteria?

I need some extra conditions on the outer join-ed table, but NHibernate always adds them to the WHERE clause at the end - which does not get the correct behaviour (see http://weblogs.sqlteam.com/jeffs/archive/2007/05/14/criteria-on-outer-joined-tables.aspx).

I can't seem to find any way to do this using Criteria or the QueryOver syntax...

Thanks

回答1:

You probably figure out this long time ago. Solution is to add ICriteria parameter in JoinAlias method, like this:

Party aliasParty = null;
Party aliasPartyFrom = null;
var parties = QueryOver.Of<Party>(() => aliasParty)
              .Left.JoinAlias(
                               () => aliasParty.AccountabilitiesFrom, 
                               () => aliasAccFrom, 
                               Restrictions.On(() => aliasAccFrom.TimeTo).IsNull)

I have restriction on aliasAccFrom, where i want that TimeTo is null, in last line of code.

回答2:

(Answered my own question - sorry!)

Fabio answered a similar query on the NHibernate list - just thought I'd post it here.

That is possible with Criteria since NH3.0. The feature in HQL http://fabiomaulo.blogspot.com/2009/05/nhibernate-210-hql-with-clause.html

With Criteria have a look to CreateAlias(string associationPath, string alias, JoinType joinType, ICriterion withClause) CreateCriteria(string associationPath, string alias, JoinType joinType, ICriterion withClause)

With QueryOver it is not available but there's a JIRA for this here: https://nhibernate.jira.com/browse/NH-2592

回答3:

i tried the following query with query over

SystemUser systemUser= null;
SurveyRequests SurveyRequests = null;

var Query2 = Session.QueryOver<SystemUser>(() => systemUser)
               .Left.JoinAlias(() => systemUser.SurveyRequests, 
               () => surveyRequest,
               Restrictions.On(()=>surveyRequest.Survey.Id).IsIn(new object []{surveyID }))

来源：https://stackoverflow.com/questions/5410781/adding-conditions-to-outer-joins-with-nhibernate-icriteria-queryover-query