mysql - sql复杂树行

Question

我有以下查询功能。它适用于整数 id，但如果 id 是 varchar(ID:Xewi3adc)，则它不起作用。好吧，我还不知道如何让它工作，我做了很多修改，但我无法让它工作。

DROP FUNCTION IF EXISTS album_tree_connect;

DELIMITER $$

CREATE FUNCTION album_tree_connect(value varchar(32)) RETURNS INT
NOT DETERMINISTIC
READS SQL DATA
BEGIN
    DECLARE _id varchar(32);
    DECLARE _parent varchar(32);
    DECLARE _next INT;
    DECLARE CONTINUE HANDLER FOR NOT FOUND SET @id = NULL;

    SET _parent = @id;
    SET _id = -1;

    IF @id IS NULL THEN
        RETURN NULL;
    END IF;

    LOOP
        SELECT  MIN(album_id)
        INTO    @id
        FROM    album
        WHERE   sub_album_of_album_id = _parent
            AND album_id > _id;
        IF @id IS NOT NULL OR _parent = @start_with THEN
            SET @level = @level + 1;
            RETURN @id;
        END IF;
        SET @level := @level - 1;
        SELECT  album_id, sub_album_of_album_id
        INTO    _id, _parent
        FROM    album
        WHERE   album_id = _parent;
    END LOOP;   
END
$$

DELIMITER ;


## select statement to pull the tree menu

SELECT   CONCAT(REPEAT('    ', level - 1), CAST(hi.album_id AS CHAR)) AS treeitem, sub_album_of_album_id, name, user_id, level
FROM    (
        SELECT  album_tree_connect(album_id) AS id, @level AS level
        FROM    (
                SELECT  @start_with := 0,
                        @id := @start_with,
                        @level := 0
                ) vars, album
        WHERE   @id IS NOT NULL
        ) ho
JOIN    album hi
ON      hi.album_id = ho.id
where user_id = 2

Answer 1

您的函数返回类型声明为 INT，因此返回值将被强制转换为该类型。如果要返回的值(album_id 字段)不是整数，它可能会被破坏。 http://dev.mysql.com/doc/refman/5.0/en/create-procedure.html