Question

如何使用条件查询应用左连接，我只能在互联网上找到内连接条件。

        Criteria cr = this.sessionFactory.getCurrentSession().createCriteria(A.class, "a").createAlias("a.division", "division");                  
        List<A> list = cr.list();

division是A类中的实体，这是返回内部联接结果。我想在部门实体上应用左连接：

select * from A as a left join divisions as division on division.id = a.id;

表A数据：

    id  name        division_id
    1   first name  1
    3   sec name    2
    6   fourth name 2
    5   3rd name    NULL

表格划分数据：

    id  type
    1   F
    2   G

内部联接：

select * from A as a inner join division where a.division_id = division.id

内部联接结果：

+----+-------------+-------------+----+------+
| id | name        | division_id | id | type |
+----+-------------+-------------+----+------+
|  1 | first name  |           1 |  1 | F    |
|  3 | sec name    |           2 |  2 | G    |
|  6 | fourth name |           2 |  2 | G    |
+----+-------------+-------------+----+------+

左连接查询：

select * from A as a left join division on division.id = a.division_id;

左连接结果：

+----+-------------+-------------+------+------+
| id | name        | division_id | id   | type |
+----+-------------+-------------+------+------+
|  1 | first name  |           1 |    1 | F    |
|  3 | sec name    |           2 |    2 | G    |
|  6 | fourth name |           2 |    2 | G    |
|  5 | 3rd name    |        NULL | NULL | NULL |
+----+-------------+-------------+------+------+

Answer 1

如果您想要左连接，可以在createAlias中提及。默认值为inner join

Criteria cr = this.sessionFactory.getCurrentSession().createCriteria(A.class, "a")
      .createAlias("a.division", "division", CriteriaSpecification.LEFT_JOIN);     // Add join type            
List<A> list = cr.list();

CriteriaSpecification.LEFT_JOIN

Hibernate criteriaQuery - 左连接

1 个答案: