Question

我的桌面设计是

users (id, username..., parent_id)

数据

id    username      parent_id
-------------------------------
1  |  admin       | null
2  |  reseller 1  | 1
3  |  client 1    | 1
4  |  reseller 2  | 1
5  |  reseller 3  | 2
6  |  reseller 4  | 2
7  |  client 2    | 5
8  |  client 3    | 6

我希望得到id 1

的所有后代

我研究过Adjacency List，Nested List＆amp;关闭表设计，但得出的结论是基于会话的邻接列表在我的情况下会更好。

我在Hierarchical queries in MySQL

找到了一个例子

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

我尝试修改此查询以获取此结果

SELECT  group_concat(@id :=
        (
        SELECT  id
        FROM    users
        WHERE   parent_id = @id
        )) AS u
FROM    (
        SELECT  @id := 1
        ) vars
STRAIGHT_JOIN
        users
WHERE   @id IS NOT NULL

但它不起作用。这是SQLFiddle

需要帮助才能使查询正常工作。

这不是How to do the Recursive SELECT query in MySQL?的重复，因为它处理父和子之间的一对多关系，而one-to = many关系在查询中创建问题。

Answer 1

最后，我在https://dba.stackexchange.com/questions/7147/find-highest-level-of-a-hierarchical-field-with-vs-without-ctes/7161#7161

创建了@RolandoDBA建议的功能

DELIMITER $$

DROP FUNCTION IF EXISTS `siblings` $$
CREATE FUNCTION `siblings` (GivenID INT) RETURNS varchar(1024) CHARSET latin1
DETERMINISTIC
BEGIN

    DECLARE rv,q,queue,queue_children VARCHAR(1024);
    DECLARE queue_length,front_id,pos INT;

    SET rv = '';
    SET queue = GivenID;
    SET queue_length = 1;

    WHILE queue_length > 0 DO
        SET front_id = FORMAT(queue,0);
        IF queue_length = 1 THEN
            SET queue = '';
        ELSE
            SET pos = LOCATE(',',queue) + 1;
            SET q = SUBSTR(queue,pos);
            SET queue = q;
        END IF;
        SET queue_length = queue_length - 1;

        SELECT IFNULL(qc,'') INTO queue_children
        FROM (SELECT GROUP_CONCAT(id) qc
        FROM `users` WHERE parent_id = front_id) A;

        IF LENGTH(queue_children) = 0 THEN
            IF LENGTH(queue) = 0 THEN
                SET queue_length = 0;
            END IF;
        ELSE
            IF LENGTH(rv) = 0 THEN
                SET rv = queue_children;
            ELSE
                SET rv = CONCAT(rv,',',queue_children);
            END IF;
            IF LENGTH(queue) = 0 THEN
                SET queue = queue_children;
            ELSE
                SET queue = CONCAT(queue,',',queue_children);
            END IF;
            SET queue_length = LENGTH(queue) - LENGTH(REPLACE(queue,',','')) + 1;
        END IF;
    END WHILE;

    RETURN rv;

END $$

然后，为了获得父母的兄弟姐妹/孩子，使用上面创建的函数siblings进行简单的调用就足够了。

SELECT siblings(id) AS `siblings` from `users` where `id` = 1

这会将结果返回为

siblings
---------------
2,3,4,5,6,7,8

平台设计中的多级层次关系（MySql）

1 个答案: