帶有內部連接的HQL查詢並檢查NULL失敗

Question

我需要選擇鏈接租借實體的所有字段return_date爲空的客戶記錄。下面的SQL查詢工作：

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; 

爲什麼以下HQL不工作：

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

語境：

@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; 
    } 

解決方案：

顯然，在使用的字段的名稱HQL必須取自模型類，但不能從數據庫中取得...

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

Answer 1

您的查詢不起作用，因爲您嘗試將客戶與集合（租賃）關聯，但要在return_date上訪問，您必須指向集合中的i-esime元素，以便您可以反轉查詢，從RENTAL對象（我希望你映射它）

試試這個：

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