具有内部连接和检查 NULL 的 HQL 查询失败

Question

我需要选择所有已链接租赁实体的客户记录，该实体的字段return_date 为空。以下 SQL 查询有效：

 SELECT
     c.customer_id, r.rental_id
     FROM
     Customer c
     INNER JOIN rental as r
     ON (c.customer_id = r.customer_id)
     WHERE r.return_date IS NULL;

为什么跟随 HQL 不起作用：

Query query = session.createQuery("from Customer customer " +
                        "inner join customer.rentals as r " +
                        "where r.return_date is null");

上下文：

@Override
    public List<Customer> getFilteredCustomers(String filter) {
        Session session = null;
        List<Customer> customers = new ArrayList<>();
            try {
                session = sessionFactory.openSession();
                Query query = session.createQuery("select customer from Customer customer " +
                        "join customer.rentals r " +
                        "where r.return_date is null");
                customers = (List<Customer>)query.list(); // << BREAKPOINT A
            }catch (Exception e){
                System.out.println(e);
            }finally {
                if (session!=null) session.close();
            }
        return customers;
    }

解决方案：

显然，HQL 中使用的字段名称必须取自模型类，而不是数据库...

Query query = session.createQuery("select c " +
                        " from Rental r, Customer c " +
                        " where r.customer = c " +
                        " and r.returnDate is null");

Answer 1

您的查询不起作用，因为您尝试将客户与集合（租赁）链接，但要在 return_date 访问，您必须指向集合的 i-esime 元素，以便您可以反转查询，从 RENTAL 开始对象（我希望你已经映射了它）

试试这个：

Query query = session.createQuery("select c " +
           " from Rental r, Customer c " +
           " where r.customer_id = c.customer_id " +
           " and r.return_date is null");