MySQL优化总结+自定义函数之递归

我最近看MySQL优化总结几个可能容易理解错误的技巧：

• 通常来说把可为 NULL 的列改为 NOT NULL 不会对性能提升有多少帮助，只是如果计划在列上创建索引，就应该将该列设置为 NOT NULL。

• 对整数类型指定宽度，比如 INT(11)，没有任何卵用。INT 使用 32 位（4 个字节）存储空间，那么它的表示范围已经确定，所以 INT(1) 和 INT(20) 对于存储和计算是相同的。

• UNSIGNED 表示不允许负值，大致可以使正数的上限提高一倍。比如 TINYINT 存储范围是 -128 ~ 127，而 UNSIGNED TINYINT 存储的范围却是 0 - 255。

• 通常来讲，没有太大的必要使用 DECIMAL 数据类型。即使是在需要存储财务数据时，仍然可以使用 BIGINT。

MySQL 查看版本号:

• mysql -V

进入MySQL查看版本号：

• SELECT VERSION();
• STATUS;

我的是8.0 的，已经亲测过 可以直接复制粘贴，直接上代码、截图。

1CREATE TABLE `t_areainfo` (
2	id INT(11) NOT NULL AUTO_INCREMENT,
3	level INT (11) DEFAULT '0',
4	name VARCHAR (255) DEFAULT '0',
5	parentId INT (11) DEFAULT '0',
6	status INT (11) DEFAULT '0',
7	PRIMARY KEY (`id`)
8) ENGINE = INNODB AUTO_INCREMENT = 65 DEFAULT CHARSET = utf8;
9
10
11INSERT INTO `t_areainfo` VALUES ('1', '0', '中国', '0', '0');
12INSERT INTO `t_areainfo` VALUES ('2', '0', '华北区', '1', '0');
13INSERT INTO `t_areainfo` VALUES ('3', '0', '华南区', '1', '0');
14INSERT INTO `t_areainfo` VALUES ('4', '0', '北京', '2', '0');
15INSERT INTO `t_areainfo` VALUES ('5', '0', '海淀区', '4', '0');
16INSERT INTO `t_areainfo` VALUES ('6', '0', '丰台区', '4', '0');
17INSERT INTO `t_areainfo` VALUES ('7', '0', '朝阳区', '4', '0');
18INSERT INTO `t_areainfo` VALUES ('8', '0', '北京XX区1', '4', '0');
19INSERT INTO `t_areainfo` VALUES ('9', '0', '北京XX区2', '4', '0');
20INSERT INTO `t_areainfo` VALUES ('10', '0', '北京XX区3', '4', '0');
21INSERT INTO `t_areainfo` VALUES ('11', '0', '北京XX区4', '4', '0');
22INSERT INTO `t_areainfo` VALUES ('12', '0', '北京XX区5', '4', '0');
23INSERT INTO `t_areainfo` VALUES ('13', '0', '北京XX区6', '4', '0');
24INSERT INTO `t_areainfo` VALUES ('14', '0', '北京XX区7', '4', '0');
25INSERT INTO `t_areainfo` VALUES ('15', '0', '北京XX区8', '4', '0');
26INSERT INTO `t_areainfo` VALUES ('16', '0', '北京XX区9', '4', '0');
27INSERT INTO `t_areainfo` VALUES ('17', '0', '北京XX区10', '4', '0');
28INSERT INTO `t_areainfo` VALUES ('18', '0', '北京XX区11', '4', '0');
29INSERT INTO `t_areainfo` VALUES ('19', '0', '北京XX区12', '4', '0');
30INSERT INTO `t_areainfo` VALUES ('20', '0', '北京XX区13', '4', '0');
31INSERT INTO `t_areainfo` VALUES ('21', '0', '北京XX区14', '4', '0');
32INSERT INTO `t_areainfo` VALUES ('22', '0', '北京XX区15', '4', '0');
33INSERT INTO `t_areainfo` VALUES ('23', '0', '北京XX区16', '4', '0');
34INSERT INTO `t_areainfo` VALUES ('24', '0', '北京XX区17', '4', '0');
35INSERT INTO `t_areainfo` VALUES ('25', '0', '北京XX区18', '4', '0');
36INSERT INTO `t_areainfo` VALUES ('26', '0', '北京XX区19', '4', '0');
37INSERT INTO `t_areainfo` VALUES ('27', '0', '北京XX区1', '4', '0');
38INSERT INTO `t_areainfo` VALUES ('28', '0', '北京XX区2', '4', '0');
39INSERT INTO `t_areainfo` VALUES ('29', '0', '北京XX区3', '4', '0');
40INSERT INTO `t_areainfo` VALUES ('30', '0', '北京XX区4', '4', '0');
41INSERT INTO `t_areainfo` VALUES ('31', '0', '北京XX区5', '4', '0');
42INSERT INTO `t_areainfo` VALUES ('32', '0', '北京XX区6', '4', '0');
43INSERT INTO `t_areainfo` VALUES ('33', '0', '北京XX区7', '4', '0');
44INSERT INTO `t_areainfo` VALUES ('34', '0', '北京XX区8', '4', '0');
45INSERT INTO `t_areainfo` VALUES ('35', '0', '北京XX区9', '4', '0');
46INSERT INTO `t_areainfo` VALUES ('36', '0', '北京XX区10', '4', '0');
47INSERT INTO `t_areainfo` VALUES ('37', '0', '北京XX区11', '4', '0');
48INSERT INTO `t_areainfo` VALUES ('38', '0', '北京XX区12', '4', '0');
49INSERT INTO `t_areainfo` VALUES ('39', '0', '北京XX区13', '4', '0');
50INSERT INTO `t_areainfo` VALUES ('40', '0', '北京XX区14', '4', '0');
51INSERT INTO `t_areainfo` VALUES ('41', '0', '北京XX区15', '4', '0');
52INSERT INTO `t_areainfo` VALUES ('42', '0', '北京XX区16', '4', '0');
53INSERT INTO `t_areainfo` VALUES ('43', '0', '北京XX区17', '4', '0');
54INSERT INTO `t_areainfo` VALUES ('44', '0', '北京XX区18', '4', '0');
55INSERT INTO `t_areainfo` VALUES ('45', '0', '北京XX区19', '4', '0');
56INSERT INTO `t_areainfo` VALUES ('46', '0', 'xx省1', '1', '0');
57INSERT INTO `t_areainfo` VALUES ('47', '0', 'xx省2', '1', '0');
58INSERT INTO `t_areainfo` VALUES ('48', '0', 'xx省3', '1', '0');
59INSERT INTO `t_areainfo` VALUES ('49', '0', 'xx省4', '1', '0');
60INSERT INTO `t_areainfo` VALUES ('50', '0', 'xx省5', '1', '0');
61INSERT INTO `t_areainfo` VALUES ('51', '0', 'xx省6', '1', '0');
62INSERT INTO `t_areainfo` VALUES ('52', '0', 'xx省7', '1', '0');
63INSERT INTO `t_areainfo` VALUES ('53', '0', 'xx省8', '1', '0');
64INSERT INTO `t_areainfo` VALUES ('54', '0', 'xx省9', '1', '0');
65INSERT INTO `t_areainfo` VALUES ('55', '0', 'xx省10', '1', '0');
66INSERT INTO `t_areainfo` VALUES ('56', '0', 'xx省11', '1', '0');
67INSERT INTO `t_areainfo` VALUES ('57', '0', 'xx省12', '1', '0');
68INSERT INTO `t_areainfo` VALUES ('58', '0', 'xx省13', '1', '0');
69INSERT INTO `t_areainfo` VALUES ('59', '0', 'xx省14', '1', '0');
70INSERT INTO `t_areainfo` VALUES ('60', '0', 'xx省15', '1', '0');
71INSERT INTO `t_areainfo` VALUES ('61', '0', 'xx省16', '1', '0');
72INSERT INTO `t_areainfo` VALUES ('62', '0', 'xx省17', '1', '0');
73INSERT INTO `t_areainfo` VALUES ('63', '0', 'xx省18', '1', '0');
74INSERT INTO `t_areainfo` VALUES ('64', '0', 'xx省19', '1', '0');
75
76
77select * from t_areainfo;

在MySql中创建自定义函数报错信息如下： ERROR 1418 (HY000): This function has none of DETERMINISTIC, NO SQL, or READS SQL DATA in its declaration and binary logging is enabled (you might want to use the less safe log_bin_trust_function_creators variable) ------解决办法如下：

1set global log_bin_trust_function_creators=1;
2
3
4DROP FUNCTION IF EXISTS queryChildrenAreaInfo;
5delimiter //    -- ;号变 //
6CREATE FUNCTION queryChildrenAreaInfo(areaId INT) RETURNS VARCHAR(4000)
7BEGIN
8DECLARE sTemp VARCHAR(4000);
9DECLARE sTempChd VARCHAR(4000);
10
11SET sTemp='$';
12SET sTempChd = CAST(areaId AS CHAR);
13
14WHILE sTempChd IS NOT NULL DO
15SET sTemp= CONCAT(sTemp,',',sTempChd);
16SELECT GROUP_CONCAT(id) INTO sTempChd FROM t_areainfo WHERE FIND_IN_SET(parentId,sTempChd)>0;
17END WHILE;
18RETURN sTemp;
19END;//
20delimiter ;
21
22
23SELECT queryChildrenAreaInfo(1);
24
25
26-- 查询id为"4"下面的所有节点
27SELECT * FROM t_areainfo WHERE FIND_IN_SET(id,queryChildrenAreaInfo(4));