mysql树状查询的示例分析

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– 创建表
drop table if exists t_hierarchy;
CREATE TABLE t_hierarchy (
id int(10) unsigned NOT NULL AUTO_INCREMENT,
parent int(10) unsigned NOT NULL,
PRIMARY KEY (id),
KEY ix_hierarchy_parent (parent, id)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

– 创建存储过程插入数据
DROP PROCEDURE if exists prc_fill_hierarchy;
DELIMITER $$
CREATE PROCEDURE prc_fill_hierarchy (level INT, fill INT)
BEGIN
DECLARE _level INT;
DECLARE _fill INT;
INSERT
INTO t_hierarchy (id, parent)
VALUES (1, 0);
SET _fill = 0;
WHILE _fill fill DO
INSERT
INTO t_hierarchy (parent)
VALUES (1);
SET _fill = _fill + 1;
END WHILE;
SET _fill = 1;
SET _level = 0;
WHILE _level level DO
INSERT
INTO t_hierarchy (parent)
SELECT hn.id
FROM t_hierarchy ho, t_hierarchy hn
WHERE ho.parent = 1
AND hn.id _fill;
SET _level = _level + 1;
SET _fill = _fill + POWER(fill, _level);
END WHILE;
END
$$
DELIMITER ;

– 插入数据
START TRANSACTION;
CALL prc_fill_hierarchy(3, 2);
COMMIT;

– 创建生成树的函数
DELIMITER $$
CREATE FUNCTION hierarchy_connect_by_parent_eq_prior_id(value INT) RETURNS INT
NOT DETERMINISTIC
READS SQL DATA
BEGIN
DECLARE _id INT;
DECLARE _parent INT;
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(id)
INTO @id
FROM t_hierarchy
WHERE parent = _parent
AND 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 id, parent
INTO _id, _parent
FROM t_hierarchy
WHERE id = _parent;
END LOOP;
END
$$
DELIMITER ;

– 生成 tree 的查询
SELECT CONCAT(REPEAT( — , level – 1), CAST(hi.id AS CHAR)) AS treeitem, parent, level
FROM (
SELECT hierarchy_connect_by_parent_eq_prior_id(id) AS id, @level AS level
FROM (
SELECT @start_with := 0,
@id := @start_with,
@level := 0
) vars, t_hierarchy
WHERE @id IS NOT NULL
) ho
JOIN t_hierarchy hi
ON hi.id = ho.id

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