如何快速找出父ID

無限極分類中，有這樣的需求，如何查找當前分類的所有祖先？

一般通過遞歸來實現，但是這裏有另外一種方案：

id  name    parent_id
---------------------------
1   Home        0
2   About       1
3   Contact     1
4   Legal       2
5   Privacy     4
6   Products    5
7   Support     1

SELECT T2.id, T2.name
FROM (
    SELECT
        @r AS _id,
        (SELECT @r := parent_id FROM table1 WHERE id = _id) AS parent_id,
        @l := @l + 1 AS lvl
    FROM
        (SELECT @r := 5, @l := 0) vars,
        table1 h
    WHERE @r <> 0) T1
JOIN table1 T2
ON T1._id = T2.id
ORDER BY T1.lvl DESC