MySQL中的分层查询

Question

我试图找到任何深度的特定领域的所有父母,祖父母等.例如,给定以下结构,如果我提供5,则返回的值应为1,2,3和4.

| a  | b  |
-----------
| 1  | 2  |
| 2  | 3  |
| 3  | 4  |
| 4  | 5  |
| 3  | 6  |
| 4  | 7  |

我该怎么做？

Answer 1

SELECT  @id :=
        (
        SELECT  senderid
        FROM    mytable
        WHERE   receiverid = @id
        ) AS person
FROM    (
        SELECT  @id := 5
        ) vars
STRAIGHT_JOIN
        mytable
WHERE   @id IS NOT NULL