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我有一个 MySQL 数据库，其中包含一个分层组件表（每个非顶级组件都有一个父组件）

它包括一个 SQL 函数GetParents(ComponentID)，它返回一个以逗号分隔的 parent 列表ComponentID，从直接 parent 开始并向上。这是按预期正常工作的。

我将该函数复制到GetPath(ComponentID并试图让它返回Title而不是ID，并更改顺序，使其从最高父级开始并下降，但被卡住了。我设法将顺序更改,为 a ->，并将顶级 ID (0) 更改为(Top Level)（顶级资产除外！），但无法弄清楚如何获取标题而不是 ID。

不幸的是 sqlfiddle 不喜欢DELIMITER（任何替代方案？）但下面是代码，包括满足以下示例的表模式和插入：

SELECT GetParents(11);应该返回4,1,0。这现在可以正常工作，我只是为了完整性而将其包括在内。

SELECT GetPath(11);目前返回(Top Level) -> 1 -> 4，但我想让它返回(Top Level) -> Cars -> Car 1

DROP TABLE IF EXISTS `Components`;
CREATE TABLE `Components` (
  `ComponentID` int(11) NOT NULL,
  `ParentComponentID` int(11) NOT NULL,
  `Title` varchar(250) NOT NULL

) ENGINE=InnoDB DEFAULT CHARSET=utf8;

ALTER TABLE `Components`
  ADD PRIMARY KEY (`ComponentID`);

ALTER TABLE `Components`
  MODIFY `ComponentID` int(11) NOT NULL AUTO_INCREMENT;
COMMIT;

INSERT INTO Components (ParentComponentID, Title) VALUES 
(0, 'Cars'),(0,'Trucks'),(0,'Boats');

INSERT INTO Components (ParentComponentID, Title) VALUES 
(1, 'Car 1'),(1,'Car 2'),(1,'Car 3'),(2,'Truck 1'),(3,'Boat 3');

INSERT INTO Components (ParentComponentID, Title) VALUES 
(4, 'Wheel 1'),(4,'Wheel 2'),(4,'Wheel 3'),(4,'Wheel 4');

INSERT INTO Components (ParentComponentID, Title) VALUES 
(5, 'Wheel 1'),(5,'Wheel 2'),(5,'Wheel 3'),(5,'Wheel 4');

-- Functions

DELIMITER $$

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

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

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

    WHILE queue_length > 0 DO
        SET front_id = queue;
        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(ParentComponentID) qc
        FROM Components WHERE ComponentID = front_id AND ParentComponentID!=ComponentID) 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 $$

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

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

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

    WHILE queue_length > 0 DO
        SET front_id = queue;
        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(ParentComponentID) qc
        FROM Components WHERE ComponentID = front_id AND ParentComponentID!=ComponentID) 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
                IF (queue_children = 0) THEN
                    SET rv = CONCAT('(Top Level) -> ',rv);
                ELSE
                    SET rv = CONCAT(queue_children,' -> ',rv);
                END IF;
            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 $$

DELIMITER ;

该函数将在 的上下文中调用SELECT getPath(ComponentID) FROM Components，该表可能有许多条目，因此最好有一个高效的算法！

谢谢！

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