MySQL中實現遞歸調用查詢數據（例如商品多級分類，地區多級分類等）

對於數據庫中的樹形結構數據，如地區表，有時候，我們需要知道某地區的所有下屬地區或者某地區的所有上屬地區，這時候就需要用到mysql的遞歸查詢。

1.先創建一張地區表如下：

DROP TABLE IF EXISTS `t_areainfo`;
CREATE TABLE `t_areainfo` (
 `id` int(11)  AUTO_INCREMENT,
 `level` int(11) DEFAULT 0,
 `name` varchar(255) DEFAULT '0',
 `parentId` int(11) DEFAULT 0,
 `status` int(11) DEFAULT 0,
 PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=65 DEFAULT CHARSET=utf8;

2.初始化一些數據方便後續測試：

INSERT INTO `t_areainfo` VALUES ('1', '0', '中國', '0', '0');
INSERT INTO `t_areainfo` VALUES ('2', '0', '華北區', '1', '0');
INSERT INTO `t_areainfo` VALUES ('3', '0', '華南區', '1', '0');
INSERT INTO `t_areainfo` VALUES ('4', '0', '北京', '2', '0');
INSERT INTO `t_areainfo` VALUES ('5', '0', '海淀區', '4', '0');
INSERT INTO `t_areainfo` VALUES ('6', '0', '豐臺區', '4', '0');
INSERT INTO `t_areainfo` VALUES ('7', '0', '朝陽區', '4', '0');
INSERT INTO `t_areainfo` VALUES ('8', '0', '北京XX區1', '4', '0');
INSERT INTO `t_areainfo` VALUES ('9', '0', '北京XX區2', '4', '0');
INSERT INTO `t_areainfo` VALUES ('10', '0', '北京XX區3', '4', '0');
INSERT INTO `t_areainfo` VALUES ('11', '0', '北京XX區4', '4', '0');
INSERT INTO `t_areainfo` VALUES ('12', '0', '北京XX區5', '4', '0');
INSERT INTO `t_areainfo` VALUES ('13', '0', '北京XX區6', '4', '0');
INSERT INTO `t_areainfo` VALUES ('14', '0', '北京XX區7', '4', '0');
INSERT INTO `t_areainfo` VALUES ('15', '0', '北京XX區8', '4', '0');
INSERT INTO `t_areainfo` VALUES ('16', '0', '北京XX區9', '4', '0');
INSERT INTO `t_areainfo` VALUES ('17', '0', '北京XX區10', '4', '0');
INSERT INTO `t_areainfo` VALUES ('18', '0', '北京XX區11', '4', '0');
INSERT INTO `t_areainfo` VALUES ('19', '0', '北京XX區12', '4', '0');
INSERT INTO `t_areainfo` VALUES ('20', '0', '北京XX區13', '4', '0');
INSERT INTO `t_areainfo` VALUES ('21', '0', '北京XX區14', '4', '0');
INSERT INTO `t_areainfo` VALUES ('22', '0', '北京XX區15', '4', '0');
INSERT INTO `t_areainfo` VALUES ('23', '0', '北京XX區16', '4', '0');
INSERT INTO `t_areainfo` VALUES ('24', '0', '北京XX區17', '4', '0');
INSERT INTO `t_areainfo` VALUES ('25', '0', '北京XX區18', '4', '0');
INSERT INTO `t_areainfo` VALUES ('26', '0', '北京XX區19', '4', '0');
INSERT INTO `t_areainfo` VALUES ('27', '0', '北京XX區1', '4', '0');
INSERT INTO `t_areainfo` VALUES ('28', '0', '北京XX區2', '4', '0');
INSERT INTO `t_areainfo` VALUES ('29', '0', '北京XX區3', '4', '0');
INSERT INTO `t_areainfo` VALUES ('30', '0', '北京XX區4', '4', '0');
INSERT INTO `t_areainfo` VALUES ('31', '0', '北京XX區5', '4', '0');
INSERT INTO `t_areainfo` VALUES ('32', '0', '北京XX區6', '4', '0');
INSERT INTO `t_areainfo` VALUES ('33', '0', '北京XX區7', '4', '0');
INSERT INTO `t_areainfo` VALUES ('34', '0', '北京XX區8', '4', '0');
INSERT INTO `t_areainfo` VALUES ('35', '0', '北京XX區9', '4', '0');
INSERT INTO `t_areainfo` VALUES ('36', '0', '北京XX區10', '4', '0');
INSERT INTO `t_areainfo` VALUES ('37', '0', '北京XX區11', '4', '0');
INSERT INTO `t_areainfo` VALUES ('38', '0', '北京XX區12', '4', '0');
INSERT INTO `t_areainfo` VALUES ('39', '0', '北京XX區13', '4', '0');
INSERT INTO `t_areainfo` VALUES ('40', '0', '北京XX區14', '4', '0');
INSERT INTO `t_areainfo` VALUES ('41', '0', '北京XX區15', '4', '0');
INSERT INTO `t_areainfo` VALUES ('42', '0', '北京XX區16', '4', '0');
INSERT INTO `t_areainfo` VALUES ('43', '0', '北京XX區17', '4', '0');
INSERT INTO `t_areainfo` VALUES ('44', '0', '北京XX區18', '4', '0');
INSERT INTO `t_areainfo` VALUES ('45', '0', '北京XX區19', '4', '0');
INSERT INTO `t_areainfo` VALUES ('46', '0', 'xx省1', '1', '0');
INSERT INTO `t_areainfo` VALUES ('47', '0', 'xx省2', '1', '0');
INSERT INTO `t_areainfo` VALUES ('48', '0', 'xx省3', '1', '0');
INSERT INTO `t_areainfo` VALUES ('49', '0', 'xx省4', '1', '0');
INSERT INTO `t_areainfo` VALUES ('50', '0', 'xx省5', '1', '0');
INSERT INTO `t_areainfo` VALUES ('51', '0', 'xx省6', '1', '0');
INSERT INTO `t_areainfo` VALUES ('52', '0', 'xx省7', '1', '0');
INSERT INTO `t_areainfo` VALUES ('53', '0', 'xx省8', '1', '0');
INSERT INTO `t_areainfo` VALUES ('54', '0', 'xx省9', '1', '0');
INSERT INTO `t_areainfo` VALUES ('55', '0', 'xx省10', '1', '0');
INSERT INTO `t_areainfo` VALUES ('56', '0', 'xx省11', '1', '0');
INSERT INTO `t_areainfo` VALUES ('57', '0', 'xx省12', '1', '0');
INSERT INTO `t_areainfo` VALUES ('58', '0', 'xx省13', '1', '0');
INSERT INTO `t_areainfo` VALUES ('59', '0', 'xx省14', '1', '0');
INSERT INTO `t_areainfo` VALUES ('60', '0', 'xx省15', '1', '0');
INSERT INTO `t_areainfo` VALUES ('61', '0', 'xx省16', '1', '0');
INSERT INTO `t_areainfo` VALUES ('62', '0', 'xx省17', '1', '0');
INSERT INTO `t_areainfo` VALUES ('63', '0', 'xx省18', '1', '0');
INSERT INTO `t_areainfo` VALUES ('64', '0', 'xx省19', '1', '0');

3.1向下遞歸方式查詢一個地區的下屬地區：

利用find_in_set(str,strlist)函數【簡單解釋就是該函數會返回字符str在字符串strlist中的下標號，存在下標號就從1開始】和group_concat()函數【該函數實現將查詢到的結果集以字符串的方式返回】實現遞歸查詢：

set global log_bin_trust_function_creators=TRUE; -- 修改配置，讓其臨時生效，否則創建函數會報錯

DROP FUNCTION IF EXISTS queryChildrenAreaInfo;
DELIMITER ;;
CREATE FUNCTION queryChildrenAreaInfo(areaId INT)
RETURNS VARCHAR(4000)
BEGIN
DECLARE sTemp VARCHAR(4000);
DECLARE sTempChd VARCHAR(4000);

SET sTemp='$';
SET sTempChd = CAST(areaId AS CHAR);

WHILE sTempChd IS NOT NULL DO
SET sTemp= CONCAT(sTemp,',',sTempChd);
SELECT GROUP_CONCAT(id) INTO sTempChd FROM t_areainfo WHERE FIND_IN_SET(parentId,sTempChd)>0;
END WHILE;
RETURN sTemp;
END
;;
DELIMITER ;

3.2調用上述創建的函數：

SELECT queryChildrenAreaInfo(1);

3.3再查詢id爲“4”的所有節點：

SELECT * FROM t_areainfo WHERE FIND_IN_SET(id,queryChildrenAreaInfo(4));

4.1向上遞歸查詢某地區的上屬地區：

DROP FUNCTION IF EXISTS queryChildrenAreaInfo1;
DELIMITER ;;
CREATE FUNCTION queryChildrenAreaInfo1(areaId INT)
RETURNS VARCHAR(4000)
BEGIN
DECLARE sTemp VARCHAR(4000);
DECLARE sTempChd VARCHAR(4000);

SET sTemp='$';
SET sTempChd = CAST(areaId AS CHAR);
SET sTemp = CONCAT(sTemp,',',sTempChd);

SELECT parentId INTO sTempChd FROM t_areainfo WHERE id = sTempChd;
WHILE sTempChd <> 0 DO
SET sTemp = CONCAT(sTemp,',',sTempChd);
SELECT parentId INTO sTempChd FROM t_areainfo WHERE id = sTempChd;
END WHILE;
RETURN sTemp;
END
;;
DELIMITER ;

4.2查詢id爲“8”的節點的所有上屬節點：

SELECT * from t_areainfo where FIND_IN_SET(id,queryChildrenAreaInfo1(8));