Question

我有一个查询

SELECT d.name, count(e.id) FROM department d LEFT OUTER JOIN employee e on e.department_id = d.id and e.salary > 5000

以及我如何将其转换为jpa 现在我有：

CriteriaQuery<Object[]> criteria = builder.createQuery(Object[].class); 
Root<Department> root = criteria.from(Department.class);
Path<String> name = root.get("name");
Expression<Long> empCount = builder.count(root.get("employees").get("id"));
criteria.multiselect(name,empCount);
TypedQuery<Object[]> query = em.createQuery(criteria);

我通过删除排序和分组来简化这两个示例任何人都可以告诉我如何修改我的jpa代码以获得与我的SQL查询相同的结果

提前致谢

Answer 1

你离结果不远了。问题是，AFAIK，你不能使用JPA对on子句添加任何限制。所以查询必须重写为

SELECT d.name, count(e.id) FROM department d 
LEFT OUTER JOIN employee e on e.department_id = d.id 
where (e.id is null or e.salary > 5000)

以下是未经测试的此查询的等效内容：

CriteriaQuery<Object[]> criteria = builder.createQuery(Object[].class); 
Root<Department> root = criteria.from(Department.class);
Path<String> name = root.get("name");

Join<Department, Employee> employee = root.join("employees", JoinType.LEFT);

Expression<Long> empCount = builder.count(employee.get("id"));
criteria.multiselect(name,empCount);
criteria.where(builder.or(builder.isNull(employee.get("id")),
                          builder.gt(employee.get("salary"), 5000)));

TypedQuery<Object[]> query = em.createQuery(criteria);

将sql查询转换为jpa

1 个答案: