Hibernate Learning Notes (10)-HQL Query

One, hql a pair of multi-query

Class (1) (multi) Students

/** * Implementation of classes and student internal connection * * SELECT c.*,s.* * FROM classes C INNER JOIN student S * WHERE (C.CID=S.CID) */@Testpublic void Testinnerjoin () {session = Hibernateutils.opensession (); Query query = Session.createquery ("from Classes C" + "INNER join c.students S"); List List = Query.list ();//object[]session.close ();} /** * Urgent Internal connection */@Testpublic void Testinnerjoin_fetch () {session = Hibernateutils.opensession (); Query query = Session.createquery ("from Classes C" + "INNER join fetch c.students S"); List List = Query.list ();//classessession.close ();} /** * LEFT Outer connection * SELECT c.*,s.* * FROM classes C left OUTER JOIN student S * ON (S.CID=C.CID) */@Testpublic void Testleftoutjo In () {session = Hibernateutils.opensession (); Query query = Session.createquery ("from Classes C" + "left outer join c.students S"); List List = Query.list ();//object[]session.close ();} /** * * */@Testpublic void Testleftoutjoin_fetch () {session = Hibernateutils.opensession (); Query query = Session.createquery ("from Classes C"+ "LEFT OUTER join fetch c.students S"); List List = Query.list ();//classessession.close ();} /** * Properties to query from two persisted classes * Note: A query with a constructor cannot exist with a fetch query at the same time * use fetch: I want to take classes * */@Testpublic void Testquerypropertyfromtwo () {session = Hibernateutils.opensession (); list<classstuview> classstuviews = Session.createquery ("Select New Cn.cil.domain.ClassStuView (C.name,s.name)" + "from Classes C inner join c.students S"). List (); Session.close ();

Second, HQL multi-to-many query

Student (many) (multi) courses

/** * */      @Testpublic void Testinnerjoin_fetch () {Session session = Sessionfactory.opensession (); Session.createquery ("From Student s inner join fetch s.courses C"). List (); Session.close ();} /** * Urgent LEFT OUTER connection */@Testpublic void Testleftouterjoin_fetch () {Session session = Sessionfactory.opensession (); Session.createquery ("From Student s left OUTER join fetch s.courses C"). List (); Session.close ();}

Three or one-to-many and many-to-many combinations

Class (1) (multi) Students (multi) courses

/** * Query All classes of all students for all courses */@Testpublic void TestQuery1 () {Session session = Hibernateutils.opensession (); list<classes> Classes = Session.createquery ("from Classes C inner join" + "Fetch c.students s INNER join" + "fetch s . Courses cc "). List (); Session.close ();} @Testpublic void TestQuery2 () {Session session = Hibernateutils.opensession (); list<student> classes = Session.createquery ("From Student s inner join fetch s.classes c INNER JOIN fetch s.courses CC "). List (); Session.close ();}

Practical Scenarios:

The user logs on to the system, determines the permissions that the user has, and displays the menu within the scope of the permission

According to username check the role of users according to the role of check permissions

CreateQuery ("from Privilege p INNER join fetch p.roles R INNER JOIN fetch r.users u where u.username=?")

Hibernate cannot be used when the relationship between tables is too complex, and HQL's writing can be quite cumbersome, using a view to solve the problem, with JDBC SQL

Copyright NOTICE: This article for Bo Master original article, without Bo Master permission not reproduced.

Hibernate Learning Notes (10)-HQL Query