Mysql Mariadb 遞歸查詢

Question

我有下表：

CREATE TABLE IF NOT EXISTS `tbl` (
  `id` int(12) NOT NULL,
  `name` varchar(50) NOT NULL,
  `parentid` int(12) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;

INSERT INTO `tbl` (`id`, `name`, `parentid`) VALUES
(1, 'categ 1', 0),
(2, 'xcateg 1.1', 1),
(3, 'acateg 1.2', 1),
(4, 'categ 1.2.1', 3),
(5, 'categ 2', 0),
(6, 'categ 2.1', 5);

並對其進行遞歸查詢：

WITH RECURSIVE tree_search (id, name, lvl, parentid) AS (
  SELECT   id, name, 0, parentid
  FROM tbl
  WHERE parentid = 0

  UNION ALL
    SELECT t.id, t.name,
    ts.lvl + 1, ts.id
    FROM tbl AS t
  JOIN tree_search AS ts ON t.parentid = ts.id
)
SELECT * FROM tree_search
ORDER BY parentid, lvl, name;

它可以工作並打印以下結果：

id  |    name      | lvl   | parentid |
----+--------------+-------+----------+
  1 | categ 1      |     0 |        0 |
  5 | categ 2      |     0 |        0 |
  3 | acateg 1.2   |     1 |        1 |
  2 | xcateg 1.1   |     1 |        1 |
  4 | categ 1.2.1  |     2 |        3 |
  6 | categ 2.1    |     1 |        5 |

我希望在結果中添加一個額外的列，即“parent_name”。 我該怎么做呢？

編輯添加： https : //stackoverflow.com/a/22376973/2027239這是我用來構建查詢的舊問題的答案

Answer 1

使用 tbl 的內部連接

CREATE TABLE IF NOT EXISTS `tbl` ( `id` int(12) NOT NULL, `name` varchar(50) NOT NULL, `parentid` int(12) NOT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4; INSERT INTO `tbl` (`id`, `name`, `parentid`) VALUES (1, 'categ 1', 0), (2, 'xcateg 1.1', 1), (3, 'acateg 1.2', 1), (4, 'categ 1.2.1', 3), (5, 'categ 2', 0), (6, 'categ 2.1', 5);

\n ✓\n\n ✓\n

WITH RECURSIVE tree_search (id, name, lvl, parentid) AS ( SELECT id, name, 0, parentid FROM tbl WHERE parentid = 0 UNION ALL SELECT t.id, t.name, ts.lvl + 1, ts.id FROM tbl AS t JOIN tree_search AS ts ON t.parentid = ts.id ) SELECT t.*, tb.`name` FROM tree_search t inner Join tbl tb ON t.parentid = tb.id ORDER BY parentid, lvl, t.name;

\n身份證 | 姓名 | 等級 | 父母 | 姓名      \n -: |  :---------- |  --: |  -------: |  :---------\n  3 |  acateg 1.2 |  1 |  1 | 類別 1   \n  2 |  xcateg 1.1 |  1 |  1 | 類別 1   \n  4 | 類別 1.2.1 |  2 |  3 | 類別 1.2\n  6 | 類別 2.1 |  1 |  5 | 類別 2   \n

db<> 在這里擺弄

或者使用left join來獲取所有id即使是那些沒有父級的。

 CREATE TABLE IF NOT EXISTS `tbl` ( `id` int(12) NOT NULL, `name` varchar(50) NOT NULL, `parentid` int(12) NOT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4; INSERT INTO `tbl` (`id`, `name`, `parentid`) VALUES (1, 'categ 1', 0), (2, 'xcateg 1.1', 1), (3, 'acateg 1.2', 1), (4, 'categ 1.2.1', 3), (5, 'categ 2', 0), (6, 'categ 2.1', 5);

\n ✓\n\n ✓\n

WITH RECURSIVE tree_search (id, name, lvl, parentid) AS ( SELECT id, name, 0, parentid FROM tbl WHERE parentid = 0 UNION ALL SELECT t.id, t.name, ts.lvl + 1, ts.id FROM tbl AS t JOIN tree_search AS ts ON t.parentid = ts.id ) SELECT t.*, tb.`name` FROM tree_search t LEFT Join tbl tb ON t.parentid = tb.id ORDER BY parentid, lvl, t.name;

\n身份證 | 姓名 | 等級 | 父母 | 姓名      \n -: |  :---------- |  --: |  -------: |  :---------\n  1 | 類別 1 |  0 |  0 | 空值      \n  5 | 類別 2 |  0 |  0 | 空值      \n  3 |  acateg 1.2 |  1 |  1 | 類別 1   \n  2 |  xcateg 1.1 |  1 |  1 | 類別 1   \n  4 | 類別 1.2.1 |  2 |  3 | 類別 1.2\n  6 | 類別 2.1 |  1 |  5 | 類別 2   \n

db<> 在這里擺弄