Question

我在MariaDB上使用一条RECURSIVE语句，以便在我知道产品类别唯一ID时从自引用类别表中获取产品类别路径。

这有效：

WITH RECURSIVE categories AS (
        SELECT * FROM tbl_eav_categories tec2 WHERE tec2.category_id = 1023
        UNION
        SELECT tec3.* FROM tbl_eav_categories tec3, categories AS c WHERE tec3.category_id = c.parent_category_id
        )
        SELECT GROUP_CONCAT(CONCAT(category_default_label,' [',category_id,']') ORDER BY category_id ASC SEPARATOR ' >> ') FROM categories

并返回：

Consumables [7] >> Catering Equipment and Supplies [95] >> Tea Bags [1023]

太好了。

但是现在我需要列出所有类别ID，并在第二列中列出它们的路径。我认为这只是在主类别表（'tbl_eav_categories'）表上执行SELECT并将上述查询作为子查询列放入即可。像这样：

SELECT
    @CatID := category_id AS 'cat_id',
    (
    WITH RECURSIVE categories AS (
        SELECT * FROM tbl_eav_categories tec2 WHERE tec2.category_id = @CatID
        UNION
        SELECT tec3.* FROM tbl_eav_categories tec3, categories AS c WHERE tec3.category_id = c.parent_category_id
        )
        SELECT GROUP_CONCAT(CONCAT(category_default_label,' [',category_id,']') ORDER BY category_id ASC SEPARATOR ' >> ') FROM categories
    ) 'categorypath'
FROM tbl_eav_categories;

但是，我得到的只是：

cat_id  categorypath
1   Bearings [1]
2   Bearings [1]
3   Bearings [1]
4   Bearings [1]
5   Bearings [1]
6   Bearings [1]
...

（像这样直到整个结果集的底部）。

经过研究，我确实认为它与@CatID变量在赋值之前被评估有关，但我无法解决该问题。

我在这里尝试遵循Ben English的指导：User variable in MySQL subquery，但它使我感到困惑：（

请帮助！：）

Answer 1

我相信我已经找到了答案，将整个表扫描包括在实际的CTE中：

WITH RECURSIVE category_path (id, title, path) AS
(
  SELECT category_id, category_default_label, category_default_label path FROM tbl_eav_categories WHERE parent_category_id IS NULL
  UNION ALL
  SELECT c.category_id, c.category_default_label, CONCAT(cp.path, ' [',c.parent_category_id, '] >> ', c.category_default_label) FROM category_path cp JOIN tbl_eav_categories c ON cp.id = c.parent_category_id
)
SELECT id,path FROM category_path
ORDER BY path;

用户变量未在子查询中

1 个答案: