如何创建具有左外部联接的JPA查询？

Question

SELECT t1.name AS lev1, t2.name as lev2, t3.name as lev3, t4.name as lev4 
FROM category AS t1 LEFT 
JOIN category AS t2 ON t2.parent = t1.category_id 
LEFT JOIN category AS t3 ON t3.parent = t2.category_id 
LEFT JOIN category AS t4 ON t4.parent = t3.category_id
WHERE t1.name = 'ROOT'

那么如何将此更改为jpql查询代码呢？谢谢

Answer 1

@Repository
    public interface CategoryRepository extends JpaRepository<Category, Integer> {
        @Query( value = 
        "SELECT t1.name AS lev1, t2.name as lev2, t3.name as lev3, t4.name as lev4 
        FROM category AS t1
        LEFT JOIN category AS t2 ON t2.parent = t1.category_id
        LEFT JOIN category AS t3 ON t3.parent = t2.category_id 
        LEFT JOIN category AS t4 ON t4.parent = t3.category_id
        WHERE t1.name = 'ROOT'",
         nativeQuery = true)
        List<Category> fetchCategoryDataLeftJoin();

    }