mysql入门篇

作者: GeekAmI | 来源:发表于2017-09-30 10:06 被阅读283次

「mysql优化专题」这大概是一篇最好的mysql优化入门文章（
Mysql入门篇
mysql入门篇
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knexjs 对mysql数据库进行简单的增删改查
DevOps专题
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MongoDB 入门篇
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单片机小白学步(1) 单片机的前世今生

mysql常用命令
mysql> SELECT VERSION(); 查看当前MYSQL版本
mysql> SELECT USER();查看当前用户
mysql> SELECT NOW();查看当前时间
mysql> SELECT DATABASE();查看当前数据库
MySQL的语句规范
关键字、函数名称大写
数据库名、表明、字段名小写
分号结尾
操作数据库
mysql> CREATE DATABASE t2;创建数据库
mysql> SHOW DATABASES;查看所有数据库
mysql> SHOW CREATE DATABASE t2;查看某个具体的数据库
mysql> ALTER DATABASE t2 CHARACTER SET=utf8;修改编码为utf8
mysql> DROP DATABASE IF EXISTS t2;删除数据库
mysql> SHOW WARNINGS;显示warning原因
数据类型

4.1 整型

整型

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4.2 浮点型
FLOAT[(M,D)]
DOUBLE[(M,D)]
其中M为全部位数，D为小数点位数

4.3 日期时间型

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4.4 字符型

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表格常用操作
$ mysql -uroot -p123456 -P3306 -h127.0.0.1;
mysql> USE test;打开数据库
mysql> SHOW TABLES;查看数据库有哪些表格
mysql> SHOW TABLES FROM mysql;查看mysql数据库的表格
mysql> CREATE TABLE tb1(
-> username varchar(20),
-> age tinyint unsigned,
-> salary FLOAT(8,2)
-> );
mysql> SHOW COLUMNS FROM tb1;查看数据表结构
mysql> INSERT INTO tb1(username, age, salary) values('xiaoming', 21, 123.3);插入记录
mysql> CREATE TABLE tb2(
-> username VARCHAR(20) NOT NULL,
-> age TINYINT NOT NULL,
-> salary FLOAT(8,2) NOT NULL
-> );
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CREATE TABLE tb6(
id BIGINT NOT NULL AUTO_INCREMENT PRIMARY KEY,
username VARCHAR(20) NOT NULL,
age TINYINT NOT NULL,
salary FLOAT(8,2) NOT NULL
);
必须定义为主键，才可以为auto_increment
auto_increment默认情况下，起始值为1，每次的增量为1
每张表只能存在一个主键，主键保证记录唯一性，主键自动为NOT NULL
mysql> CREATE TABLE tb10(
-> id BIGINT NOT NULL AUTO_INCREMENT PRIMARY KEY,
-> username VARCHAR(20) NOT NULL UNIQUE,
-> age TINYINT DEFAULT 20
-> );
mysql> INSERT INTO tb10(username) VALUES('小明');
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UNIQUE KEY:唯一约束，可以保证记录唯一性，每张表可以存在多个唯一约束；
DEFAULT：默认值；

创建外键约束

CREATE TABLE province(
id SMALLINT NOT NULL AUTO_INCREMENT PRIMARY KEY,
name VARCHAR(20) NOT NULL 
)ENGINE=INNODB CHARSET=utf8;

CREATE TABLE user(
 id BIGINT NOT NULL AUTO_INCREMENT PRIMARY KEY,
 username VARCHAR(20) NOT NULL,
 province_id SMALLINT NOT NULL,
 FOREIGN KEY (province_id) REFERENCES province(id)
 )ENGINE=InnoDB DEFAULT CHARSET=utf8;

外键约束的要求：
父表和子表使用相同的存储引擎，数据表的存储引擎只能为InNODB；
外键列和参照列必须具有相似的数据类型。其中数字的长度和符号位必须相同，而字符的长度则可以不同；
外键列和参照列必须创建索引。如果外键列不存在索引的话，MySQL将自动创建索引。

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外键约束的参照操作：
CASCADE:从父表删除或更新且自动删除或更新子表中匹配的行
SET NULL:从父表删除或更新行，会设置子表中的外键列为NULL。必须保证子表外键列没有指定NOT NULL；
RESTRICT:拒绝对父表的删除或更新操作；
NO ACTION:标准SQL关键字，在MySQL中与RESTRICT相同。

mysql> CREATE TABLE user1(
-> id BIGINT NOT NULL AUTO_INCREMENT PRIMARY KEY,
-> username VARCHAR(20) NOT NULL,
-> province_id SMALLINT NOT NULL,
-> FOREIGN KEY (province_id) REFERENCES province(id) ON DELETE CASCADE
-> )ENGINE=InnoDB DEFAULT CHARSET=utf8;
mysql> INSERT INTO province(name) values('henan');
mysql> INSERT INTO province(name) values('shandong');
mysql> INSERT INTO province(name) values('shanghai');

mysql> INSERT INTO user1(username, province_id) VALUES('ROSE', 1);
mysql> INSERT INTO user1(username, province_id) VALUES('JACK', 3);
mysql> INSERT INTO user1(username, province_id) VALUES('TOM', 3);

mysql> INSERT INTO user1(username, province_id) VALUES('BLUZE', 7);
ERROR 1452 (23000): Cannot add or update a child row: a foreign key constraint fails (test.user1, CONSTRAINT user1_ibfk_1 FOREIGN KEY (province_id) REFERENCES province (id) ON DELETE CASCADE)

mysql> DELETE FROM province WHERE id=3;

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修改表格字段
mysql> ALTER TABLE user1 ADD score BIGINT NOT NULL FIRST;在表格首部增加一个字段；
mysql> ALTER TABLE user1 ADD password VARCHAR(20) NOT NULL AFTER username;在username后面增加一个字段；
mysql> ALTER TABLE user1 DROP score;删除一个字段
修改约束

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添加主键约束：
mysql> ALTER TABLE tb1 ADD PRIMARY KEY(username);

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添加唯一约束：
mysql> ALTER TABLE tb1 ADD UNIQUE KEY(age);

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删除主键/唯一约束：
mysql> ALTER TABLE tb1 DROP PRIMARY KEY;

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mysql> ALTER TABLE tb1 DROP INDEX age;

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添加删除默认约束
mysql> ALTER TABLE tb1 ALTER age SET DEFAULT 3;

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mysql> ALTER TABLE tb1 ALTER age DROP DEFAULT;

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删除外键约束：

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mysql> ALTER TABLE user1 DROP FOREIGN KEY user1_ibfk_1;

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修改列定义：

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mysql> ALTER TABLE user1 MODIFY id BIGINT NOT NULL AUTO_INCREMENT FIRST;

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修改列名字：

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mysql> ALTER TABLE user1 CHANGE username user_name VARCHAR(20) NOT NULL;

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修改表名字：
mysql> ALTER TABLE user1 RENAME user2;

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操作数据表中的记录

9.1 插入记录：
mysql> CREATE TABLE users(
-> id SMALLINT AUTO_INCREMENT PRIMARY KEY,
-> username VARCHAR(20) NOT NULL,
-> password VARCHAR(20) NOT NULL,
-> age TINYINT NOT NULL DEFAULT 10,
-> sex BOOLEAN NOT NULL
-> )ENGINE=INNODB DEFAULT CHARSET=utf8;
mysql> INSERT INTO users VALUES(NULL, 'xiaoming', '123', 22, 1);
mysql> INSERT INTO users VALUES(DEFAULT, 'jack', '123', 22, 1);
mysql> INSERT INTO users VALUES(DEFAULT, 'rose', '123', DEFAULT, 1);
mysql> INSERT INTO users VALUES(DEFAULT, 'bluze', '123', DEFAULT, 1),(DEFAULT, 'huahua', '321', 32, 0);
mysql> INSERT INTO users(username, password, sex) VALUES('niuniu', '643', 0),('gougou', '777', 1);

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mysql> INSERT INTO users SET username='haha', password='321', sex=0;

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9.2 更新记录操作
mysql> UPDATE users SET age = age + 5;

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mysql> UPDATE users SET age = age -10, sex = 0;

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mysql> UPDATE users SET age = age - id;

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mysql> UPDATE users SET age = age + 10 where id % 2 = 0;

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9.3 删除一条记录
mysql> DELETE FROM users WHERE id=6;

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mysql> INSERT INTO users VALUES(DEFAULT, 'TOM', '2323', DEFAULT, 1);

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9.4 查找记录
mysql> SELECT id, username FROM users;

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mysql> SELECT username, id FROM users;

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mysql> SELECT id AS user_id, username AS user_name FROM users;

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mysql> SELECT users.id, users.username FROM users;

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mysql> SELECT sex FROM users GROUP BY sex;

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mysql> SELECT sex FROM users GROUP BY sex ASC;

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mysql> SELECT sex FROM users GROUP BY sex DESC;

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mysql> SELECT sex,age FROM users GROUP BY sex HAVING age>7;

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mysql> SELECT * FROM users ORDER BY age DESC;

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mysql> SELECT * FROM users ORDER BY age DESC,id DESC;

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mysql> SELECT * FROM users LIMIT 2;

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mysql> SELECT * FROM users LIMIT 2,3;

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mysql> SELECT * FROM users ORDER BY id DESC LIMIT 2,3;

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mysql> CREATE TABLE test(
-> id SMALLINT AUTO_INCREMENT PRIMARY KEY,
-> username VARCHAR(20) NOT NULL
-> )CHARSET=utf8;
mysql> INSERT INTO test(username) SELECT username FROM users;

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子查询与连接
10.1数据准备

mysql>  CREATE TABLE IF NOT EXISTS tbd_goods(
    -> goods_id SMALLINT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
    -> goods_name varchar(150) NOT NULL,
    -> goods_cate VARCHAR(40) NOT NULL,
    -> brand_name VARCHAR(40) NOT NULL,
    -> goods_price DECIMAL(15,3) UNSIGNED NOT NULL DEFAULT 0,
    -> is_show BOOLEAN NOT NULL DEFAULT 1,
    -> is_saleoff BOOLEAN NOT NULL DEFAULT 0
    -> )CHARSET=utf8;

 INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('R510VC 15.6英寸笔记本','笔记本','华硕','3399',DEFAULT,DEFAULT);
 
 INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('Y400N 14.0英寸笔记本电脑','笔记本','联想','4899',DEFAULT,DEFAULT);
 
 INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('G150TH 15.6英寸游戏本','游戏本','雷神','8499',DEFAULT,DEFAULT);
 
 INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('X550CC 15.6英寸笔记本','笔记本','华硕','2799',DEFAULT,DEFAULT);
 
 INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('X240(20ALA0EYCD) 12.5英寸超极本','超级本','联想','4999',DEFAULT,DEFAULT);
 
 INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('U330P 13.3英寸超极本','超级本','联想','4299',DEFAULT,DEFAULT);
 
 INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('SVP13226SCB 13.3英寸触控超极本','超级本','索尼','7999',DEFAULT,DEFAULT);
 
 INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('iPad mini MD531CH/A 7.9英寸平板电脑','平板电脑','苹果','1998',DEFAULT,DEFAULT);
 
 INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('iPad Air MD788CH/A 9.7英寸平板电脑 （16G WiFi版）','平板电脑','苹果','3388',DEFAULT,DEFAULT);
 
 INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES(' iPad mini ME279CH/A 配备 Retina 显示屏 7.9英寸平板电脑 （16G WiFi版）','平板电脑','苹果','2788',DEFAULT,DEFAULT);
 
 INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('IdeaCentre C340 20英寸一体电脑 ','台式机','联想','3499',DEFAULT,DEFAULT);
 
 INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('Vostro 3800-R1206 台式电脑','台式机','戴尔','2899',DEFAULT,DEFAULT);
 
 INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('iMac ME086CH/A 21.5英寸一体电脑','台式机','苹果','9188',DEFAULT,DEFAULT);
 
 INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('AT7-7414LP 台式电脑 （i5-3450四核 4G 500G 2G独显 DVD 键鼠 Linux ）','台式机','宏碁','3699',DEFAULT,DEFAULT);
 
 INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('Z220SFF F4F06PA工作站','服务器/工作站','惠普','4288',DEFAULT,DEFAULT);
 
 INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('PowerEdge T110 II服务器','服务器/工作站','戴尔','5388',DEFAULT,DEFAULT);
 
 INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('Mac Pro MD878CH/A 专业级台式电脑','服务器/工作站','苹果','28888',DEFAULT,DEFAULT);
 
 INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES(' HMZ-T3W 头戴显示设备','笔记本配件','索尼','6999',DEFAULT,DEFAULT);

 INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('商务双肩背包','笔记本配件','索尼','99',DEFAULT,DEFAULT);

 INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('X3250 M4机架式服务器 2583i14','服务器/工作站','IBM','6888',DEFAULT,DEFAULT);
 
 INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('玄龙精英版 笔记本散热器','笔记本配件','九州风神','',DEFAULT,DEFAULT);

 INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES(' HMZ-T3W 头戴显示设备','笔记本配件','索尼','6999',DEFAULT,DEFAULT);

 INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('商务双肩背包','笔记本配件','索尼','99',DEFAULT,DEFAULT);

10.2 比较运算符子查询
mysql> SELECT goods_id, goods_name,goods_price FROM tdb_goods WHERE goods_price > (SELECT ROUND(AVG(goods_price)) FROM tdb_goods);

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mysql> SELECT goods_id, goods_name, goods_price FROM tdb_goods WHERE goods_cate='超级本';

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mysql> SELECT goods_id,goods_price FROM tdb_goods WHERE goods_price > ANY(SELECT goods_price FROM tdb_goods WHERE goods_cate='超级本');

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mysql> SELECT goods_id,goods_price FROM tdb_goods WHERE goods_price = ANY(SELECT goods_price FROM tdb_goods WHERE goods_cate='超级本');

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mysql> SELECT goods_id,goods_price FROM tdb_goods WHERE goods_price <> ALL(SELECT goods_price FROM tdb_goods WHERE goods_cate='超级本');

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10.3 NOT IN子查询
mysql> mysql> SELECT goods_id,goods_price FROM tdb_goods WHERE goods_price IN (SELECT goods_price FROM tdb_goods WHERE goods_cate='超级本');

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mysql> mysql> SELECT goods_id,goods_price FROM tdb_goods WHERE goods= ANY(SELECT goods_price FROM tdb_goods WHERE goods_cate='超级本');

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mysql> SELECT goods_id,goods_price FROM tdb_goods WHERE goods_price NOT IN (SELECT goods_price FROM tdb_goods WHERE goods_cate='超级本');

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mysql> SELECT goods_id,goods_price FROM tdb_goods WHERE goods_price <>ALL(SELECT goods_price FROM tdb_goods WHERE goods_cate='超级本');

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10.4 插入子句
mysql> CREATE TABLE tdb_goods_cate(
-> id SMALLINT UNSIGNED PRIMARY KEY AUTO_INCREMENT,
-> goods_cate VARCHAR(40) NOT NULL
-> )CHARSET=utf8;

mysql> INSERT INTO tdb_goods_cate(goods_cate) SELECT goods_cate FROM tdb_goods GROUP BY goods_cate;

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10.5 多表连接
mysql> UPDATE tdb_goods INNER JOIN tdb_goods_cate ON tdb_goods.goods_cate = tdb_goods_cate.goods_cate SET tdb_goods.goods_cate = id;

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mysql> CREATE TABLE tdb_goods_brand(
-> id SMALLINT UNSIGNED PRIMARY KEY AUTO_INCREMENT,
-> brand_name VARCHAR(40) NOT NULL
-> )
-> SELECT brand_name FROM tdb_goods GROUP BY brand_name;

mysql> UPDATE tdb_goods AS t INNER JOIN tdb_goods_brand AS g ON t.brand_name = g.brand_name SET t.brand_name = g.id;

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mysql> ALTER TABLE tdb_goods CHANGE goods_cate cate_id SMALLINT UNSIGNED NOT NULL,CHANGE brand_name brand_id SMALLINT UNSIGNED NOT NULL;

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mysql> INSERT tdb_goods_cate(goods_cate) VALUES('路由器'),('交换机'),('网卡');
mysql> INSERT tdb_goods(goods_name,cate_id,brand_id,goods_price) VALUES(' LaserJet Pro P1606dn 黑白激光打印机','12','4','1849');

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内连接：

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mysql> SELECT goods_id,goods_name,goods_cate FROM tdb_goods INNER JOIN tdb_goods_cate ON cate_id = id;

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左外连接：

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mysql> SELECT goods_id,goods_name,goods_cate FROM tdb_goods LEFT JOIN tdb_goods_cate ON cate_id = id;

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右外连接：

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mysql> SELECT goods_id,goods_name,goods_cate FROM tdb_goods RIGHT JOIN tdb_goods_cate ON cate_id = id;

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多表连接举例：
mysql> SELECT goods_id,goods_name,goods_cate,brand_name FROM tdb_goods AS t
INNER JOIN tdb_goods_cate as g ON t.cate_id = g.id
INNER JOIN tdb_goods_brand AS b ON t.brand_id = b.id;

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自身连接：
CREATE TABLE tdb_goods_types(
type_id SMALLINT UNSIGNED PRIMARY KEY AUTO_INCREMENT,
type_name VARCHAR(20) NOT NULL,
parent_id SMALLINT UNSIGNED NOT NULL DEFAULT 0
);
INSERT tdb_goods_types(type_name,parent_id) VALUES('家用电器',DEFAULT);
INSERT tdb_goods_types(type_name,parent_id) VALUES('电脑、办公',DEFAULT);
INSERT tdb_goods_types(type_name,parent_id) VALUES('大家电',1);
INSERT tdb_goods_types(type_name,parent_id) VALUES('生活电器',1);
INSERT tdb_goods_types(type_name,parent_id) VALUES('平板电视',3);
INSERT tdb_goods_types(type_name,parent_id) VALUES('空调',3);
INSERT tdb_goods_types(type_name,parent_id) VALUES('电风扇',4);
INSERT tdb_goods_types(type_name,parent_id) VALUES('饮水机',4);
INSERT tdb_goods_types(type_name,parent_id) VALUES('电脑整机',2);
INSERT tdb_goods_types(type_name,parent_id) VALUES('电脑配件',2);
INSERT tdb_goods_types(type_name,parent_id) VALUES('笔记本',9);
INSERT tdb_goods_types(type_name,parent_id) VALUES('超级本',9);
INSERT tdb_goods_types(type_name,parent_id) VALUES('游戏本',9);
INSERT tdb_goods_types(type_name,parent_id) VALUES('CPU',10);
INSERT tdb_goods_types(type_name,parent_id) VALUES('主机',10);
-- 查找所有分类及其父类
mysql> SELECT s.type_id, s.type_name, p.type_name FROM tdb_goods_types AS s LEFT JOIN tdb_goods_types AS p ON s.parent_id = p.type_id;

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-- 查找所有分类及其子类
mysql> SELECT p.type_id,p.type_name,s.type_name FROM tdb_goods_types AS p LEFT JOIN tdb_goods_types s ON s.parent_id=p.type_id;

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-- 查找所有分类及其子类数目
mysql> SELECT p.type_id,p.type_name,COUNT(s.type_name) FROM tdb_goods_types AS p LEFT JOIN tdb_goods_types s ON s.parent_id=p.type_id GROUP BY p.type_name ORDER BY type_id;

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--删除重复记录
mysql> SELECT goods_id, goods_name FROM tdb_goods GROUP BY(goods_name) HAVING COUNT(goods_name)>=2;

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DELETE t1 FROM tdb_goods AS t1 LEFT JOIN (SELECT goods_id,goods_name FROM tdb_goods GROUP BY(goods_name) HAVING COUNT(goods_name)>=2) AS t2 ON t1.goods_name=t2.goods_name WHERE t1.goods_id > t2.goods_id;

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11 存储过程
11.1 不带参数的存储过程
mysql> CREATE PROCEDURE sp1() SELECT VERSION();
mysql> CALL sp1();

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mysql> CALL sp1;

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11.2 带IN参数的存储过程
mysql> DELIMITER //
mysql> CREATE PROCEDURE removeUserById(IN USER_ID INT UNSIGNED)
-> BEGIN
-> DELETE FROM users WHERE id = USER_ID;
-> END
-> //
mysql> DELIMITER ;

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mysql> CALL removeUserById(2);

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mysql> DROP PROCEDURE removeUserById;删除存储过程

11.3 创建带IN和OUT类型的存储过程

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mysql> DELIMITER //
mysql> CREATE PROCEDURE removeUserAndReturnNums(IN p_id INT UNSIGNED, OUT nums INT UNSIGNED)
-> BEGIN
-> DELETE FROM users WHERE id = p_id;
-> SELECT COUNT(id) FROM users INTO nums;
-> END
-> //
mysql> DELIMITER ;
mysql> CALL removeUserAndReturnNums(3, @num);

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11.4 创建带IN和多个OUT类型的存储过程

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mysql> CREATE PROCEDURE removeUserByAgeAndReturnInfos(IN delAge SMALLINT UNSIGNED, OUT delNum SMALLINT UNSIGNED, OUT restNum SMALLINT UNSIGNED)
-> BEGIN
-> DELETE FROM users WHERE age = delAge;
-> SELECT ROW_COUNT() INTO delNum;
-> SELECT COUNT(id) FROM users INTO restNum;
-> END
-> //
mysql> DELIMITER ;
mysql> CALL removeUserByAgeAndReturnInfos(10,@delNum,@restNum);

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mysql> DROP PROCEDURE removeUserByAgeAndReturnInfos;

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