一、启动/关闭MYSQL服务
net start mysql
D:\>net start mysql
MySQL 服务正在启动 ..
MySQL 服务已经启动成功。
net stop mysql
C:\WINDOWS\system32>net stop mysql
MySQL 服务正在停止
二、登录和退出MYSQL
//登录方法1
D:\>mysql -u root -p
Enter password: ********
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 2
//登录方法2
D:\>mysql -u root -p -P3306 -h 127.0.0.1
C:\WINDOWS\system32>mysql -u root -p -P3306 -h 127.0.0.1
Enter password: ********
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 13
Server version: 5.7.22 MySQL Community Server (GPL)
//退出
mysql>exit;
mysql>quit;
mysql>\q;
三、修改提示符
prompt
D:\>mysql -u root -p root -prompt \h(服务器名称localhost)
mysql>prompt \h(服务器名称localhost);
MYSQL提示符
\D 完整的日期
\d 当前数据库
\h 服务器名称
\u 当前用户
\u@\h \d>
当前用户@服务器名称 当前数据库>
四、MYSQL常用命令和语法规范
1、显示当前服务器版本
mysql> SELECT VERSION();
+-----------+
| VERSION() |
+-----------+
| 5.7.22 |
+-----------+
1 row in set (0.12 sec)
2、显示当前日期时间
mysql> SELECT NOW();
+---------------------+
| NOW() |
+---------------------+
| 2018-07-24 15:26:22 |
+---------------------+
1 row in set (0.05 sec)
3、显示当前用户
mysql> SELECT USER();
+----------------+
| USER() |
+----------------+
| root@localhost |
+----------------+
1 row in set (0.03 sec)
4、MySQL语句规范
1）、关键字与函数名称全部大写（小写可以执行，为了区分关键字）
2）、数据库名称、表名称、字段名称全部小写
3）、SQL语句必须以分号结尾
五、操作数据库
{}:必选项
[]：可选项
1、创建数据库
CREATE {DATABASE|SCHEMA} [IF NOT EXISTS] db_name
[DEFAULT] CHARACTER SET [=] charset_name
mysql> CREATE DATABASE t1;
Query OK, 1 row affected (0.07 sec)
//创建已存在的数据库
mysql> CREATE DATABASE t1;
ERROR 1007 (HY000): Can't create database 't1'; database exists
//显示错误信息
mysql> SHOW WARNINGS;
+-------+------+---------------------------------------------+
| Level | Code | Message |
+-------+------+---------------------------------------------+
| Error | 1007 | Can't create database 't1'; database exists |
+-------+------+---------------------------------------------+
1 row in set (0.00 sec)
//显示数据库属性
mysql> SHOW CREATE DATABASE t1;
+----------+-------------------------------------------------------------+
| Database | Create Database |
+----------+-------------------------------------------------------------+
| t1 | CREATE DATABASE `t1` /*!40100 DEFAULT CHARACTER SET utf8 */ |
+----------+-------------------------------------------------------------+
1 row in set (0.14 sec)
2、显示数据库列表
mysql> SHOW DATABASES;
+--------------------+
| Database |
+--------------------+
| information_schema |
| bluedot |
| kdd |
| mysql |
| performance_schema |
| sys |
| t1 |
+--------------------+
7 rows in set (0.32 sec)
3、修改数据库
ALTER {DATABASE|SCHEMA} [db_name]
[DEFAULT] CHARACTER SET [=] charset_name
//修改数据库t1的编码为gbk
mysql> ALTER DATABASE t1 CHARACTER SET = gbk;
Query OK, 1 row affected (0.18 sec)
mysql> SHOW CREATE DATABASE t1;
+----------+------------------------------------------------------------+
| Database | Create Database |
+----------+------------------------------------------------------------+
| t1 | CREATE DATABASE `t1` /*!40100 DEFAULT CHARACTER SET gbk */ |
+----------+------------------------------------------------------------+
1 row in set (0.00 sec)
4、删除数据库
mysql> DROP DATABASE t1;
Query OK, 0 rows affected (1.32 sec)
mysql> SHOW DATABASES;
+--------------------+
| Database |
+--------------------+
| information_schema |
| bluedot |
| kdd |
| mysql |
| performance_schema |
| sys |
+--------------------+
6 rows in set (0.00 sec)
//删除已经删除的数据库
mysql> DROP DATABASE t1;
ERROR 1008 (HY000): Can't drop database 't1'; database doesn't exist
mysql> SHOW WARNINGS;
+-------+------+--------------------------------------------------+
| Level | Code | Message |
+-------+------+--------------------------------------------------+
| Error | 1008 | Can't drop database 't1'; database doesn't exist |
+-------+------+--------------------------------------------------+
1 row in set (0.00 sec)
六、数据类型
1、基本类型
整型int、浮点型float、双精度浮点 double
2、日期时间型
3、字符型
七、数据表的操作
1、创建数据表
打开数据库
USE 数据库名称；
mysql> USE t1;
Database changed
//显示打开的数据库
mysql> SELECT DATABASE();
+------------+
| DATABASE() |
+------------+
| t1 |
+------------+
1 row in set (0.00 sec)
//数据表应该事先考虑好
CREATE TABLE [IF NOT EXISTS] table_name(column_name data_type,...)
//数据表应该事先考虑好
CREATE TABLE [IF NOT EXISTS] table_name(column_name data_type,...)
mysql> CREATE TABLE tb1(
-> username VARCHAR(20),
-> age TINYINT UNSIGNED,
-> salary FLOAT(8,2) UNSIGNED
-> );
Query OK, 0 rows affected (0.68 sec)
2、查看数据表
mysql> SHOW TABLES;
+--------------+
| Tables_in_t1 |
+--------------+
| tb1 |
+--------------+
1 row in set (0.00 sec)
//查看数据库的数据表列表
mysql> SHOW TABLES FROM mysql;
+---------------------------+
| Tables_in_mysql |
+---------------------------+
| columns_priv |
| db |
| engine_cost |
| event |
| func |
| general_log |
| gtid_executed |
| help_category |
| help_keyword |
| help_relation |
| help_topic |
| innodb_index_stats |
| innodb_table_stats |
| ndb_binlog_index |
| plugin |
| proc |
| procs_priv |
| proxies_priv |
| server_cost |
| servers |
| slave_master_info |
| slave_relay_log_info |
| slave_worker_info |
| slow_log |
| tables_priv |
| time_zone |
| time_zone_leap_second |
| time_zone_name |
| time_zone_transition |
| time_zone_transition_type |
| user |
+---------------------------+
31 rows in set (0.00 sec)
3、查看数据表结构
mysql> SHOW COLUMNS FROM tb1;
+----------+---------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+---------------------+------+-----+---------+-------+
| username | varchar(20) | YES | | NULL | |
| age | tinyint(3) unsigned | YES | | NULL | |
| salary | float(8,2) unsigned | YES | | NULL | |
+----------+---------------------+------+-----+---------+-------+
3 rows in set (0.01 sec)
4、记录（行）的插入和查找
插入数据
INSERT [INTO] table_name [(col_name,...)] VALUES(val,...)
//省略全部字段名，必须给全部字段赋值
mysql> INSERT tb1 VALUES('Tom',25,7819.25);
Query OK, 1 row affected (0.12 sec)
//否则,报错
mysql> INSERT tb1 VALUES('Tom',25);
ERROR 1136 (21S01): Column count doesn't match value count at row 1
//赋值部分字段
mysql> INSERT tb1(username,salary) VALUES('Tom',5600);
Query OK, 1 row affected (0.08 sec)
记录的查找
SELECT expr,... FROM table_name
//全部记录，*用来过滤字段
mysql> SELECT * FROM tb1;
+----------+------+---------+
| username | age | salary |
+----------+------+---------+
| Tom | 25 | 7819.25 |
| Tom | NULL | 5600.00 |
+----------+------+---------+
2 rows in set (0.00 sec)
5、空值和非空
NULL,字段值可以为空
NOT NULL,字段值不可以为空
mysql> CREATE TABLE tb2(
-> username VARCHAR(20) NOT NULL,
-> age TINYINT UNSIGNED NULL
-> );
Query OK, 0 rows affected (0.47 sec)
//查看数据表属性
mysql> SHOW COLUMNS FROM tb2;
+----------+---------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+---------------------+------+-----+---------+-------+
| username | varchar(20) | NO | | NULL | |
| age | tinyint(3) unsigned | YES | | NULL | |
+----------+---------------------+------+-----+---------+-------+
2 rows in set (0.00 sec)
//插入空值
mysql> INSERT tb2 VALUES('Tom',NULL);
Query OK, 1 row affected (0.07 sec)
mysql> SELECT *FROM tb2;
+----------+------+
| username | age |
+----------+------+
| Tom | NULL |
+----------+------+
1 row in set (0.00 sec)
//错误测试
mysql> INSERT tb2 VALUES(NULL,26);
ERROR 1048 (23000): Column 'username' cannot be null
6、约束
主键约束：PRIMARY KEY
每一张数据表只能存在一个 主键
主键保证了记录的唯一性
主键自动为 NOT NULL
mysql> CREATE TABLE tb3(
-> id SMALLINT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
-> username VARCHAR(30) NOT NULL
-> );
Query OK, 0 rows affected (0.57 sec)
mysql> SHOW COLUMNS FROM tb3;
+----------+----------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+----------+----------------------+------+-----+---------+----------------+
| id | smallint(5) unsigned | NO | PRI | NULL | auto_increment |
| username | varchar(30) | NO | | NULL | |
+----------+----------------------+------+-----+---------+----------------+
2 rows in set (0.00 sec)
唯一约束：UNIQUE KEY
唯一约束可以保证记录的唯一性
唯一约束的字段可以为空值（NULL）
每张数据表可以存在多个唯一约束
mysql> CREATE TABLE tb5(
-> id SMALLINT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
-> username VARCHAR(20) NOT NULL UNIQUE KEY,
-> age TINYINT UNSIGNED
-> );
Query OK, 0 rows affected (0.44 sec)
mysql> SHOW COLUMNS FROM tb5;
+----------+----------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+----------+----------------------+------+-----+---------+----------------+
| id | smallint(5) unsigned | NO | PRI | NULL | auto_increment |
| username | varchar(20) | NO | UNI | NULL | |
| age | tinyint(3) unsigned | YES | | NULL | |
+----------+----------------------+------+-----+---------+----------------+
3 rows in set (0.01 sec)
mysql> INSERT tb5(username,age) VALUES('Tom',25);
Query OK, 1 row affected (0.09 sec)
//唯一约束
mysql> INSERT tb5(username,age) VALUES('Tom',22);
ERROR 1062 (23000): Duplicate entry 'Tom' for key 'username'
默认约束：DEFAULT
mysql> CREATE TABLE tb6(
-> id SMALLINT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
-> username VARCHAR(20) NOT NULL UNIQUE KEY,
-> sex ENUM('1','2','3') DEFAULT '3'
-> );
Query OK, 0 rows affected (0.56 sec)
mysql> SHOW COLUMNS FROM tb6;
+----------+----------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+----------+----------------------+------+-----+---------+----------------+
| id | smallint(5) unsigned | NO | PRI | NULL | auto_increment |
| username | varchar(20) | NO | UNI | NULL | |
| sex | enum('1','2','3') | YES | | 3 | |
+----------+----------------------+------+-----+---------+----------------+
3 rows in set (0.01 sec)
mysql> INSERT tb6(username) VALUES('Tom');
Query OK, 1 row affected (0.09 sec)
mysql> SELECT *FROM tb6;
+----+----------+------+
| id | username | sex |
+----+----------+------+
| 1 | Tom | 3 |
+----+----------+------+
1 row in set (0.00 sec)
7、自动编号
//自动编号 AUTO_INCREMENT
mysql> CREATE TABLE tb3(
-> id SMALLINT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
-> username VARCHAR(30)
-> );
Query OK, 0 rows affected (0.38 sec)
mysql> INSERT tb3(username) VALUES('Tom');
Query OK, 1 row affected (0.10 sec)
mysql> INSERT tb3(username) VALUES('John');
Query OK, 1 row affected (0.10 sec)
mysql> INSERT tb3(username) VALUES('Rose');
Query OK, 1 row affected (0.10 sec)
mysql> INSERT tb3(username) VALUES('Dimitar');
Query OK, 1 row affected (0.10 sec)
mysql> SELECT *FROM tb3;
+----+----------+
| id | username |
+----+----------+
| 1 | Tom |
| 2 | John |
| 3 | Rose |
| 4 | Dimitar |
+----+----------+
4 rows in set (0.00 sec)
//非自动编号
mysql> CREATE TABLE tb4(
-> id SMALLINT UNSIGNED PRIMARY KEY,
-> username VARCHAR(30)
-> );
Query OK, 0 rows affected (0.38 sec)
mysql> SHOW COLUMNS FROM tb4;
+----------+----------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+----------------------+------+-----+---------+-------+
| id | smallint(5) unsigned | NO | PRI | NULL | |
| username | varchar(30) | YES | | NULL | |
+----------+----------------------+------+-----+---------+-------+
2 rows in set (0.00 sec)
mysql> INSERT tb4 VALUES(22,'Tom');
Query OK, 1 row affected (0.16 sec)
mysql> INSERT tb4 VALUES(4,'John');
Query OK, 1 row affected (0.10 sec)
mysql> SELECT *FROM tb4;
+----+----------+
| id | username |
+----+----------+
| 22 | Tom |
| 4 | John |
+----+----------+
2 rows in set (0.00 sec)
八、约束和修改数据表
1)、约束保证了数据的完整性和一致性
2)、约束分为表级约束和列级约束
3)、约束的类型包括：
NOT NULL(非空约束) PRIMARY KEY(主键约束) UNIQUE KEY(唯一约束)
DEFAUT(默认约束) FOREIIGN KEY(外键约束)
1、外键约束：FOREIIGN KEY
保证数据一致性
实现一对一一对多关系
外键约束要求：
1)、父表和字表必须具有相同的存储引擎，禁止使用临时表
2)、数据表的存储引擎只能为InnoDB
3)、外键列和参照列必须具有相似的数据类型。其中数字的长度或是否有符号位必须相同，而字符的长度可以不同
4)、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
编辑数据表的默认存储 引擎
MYSQL配置文件
# 创建新表时将使用的默认存储引擎
default-storage-engine=INNODB
2、外键约束的参照操作
1)、CASCADE:从父表删除和更新且自动更新子表中匹配的行
2)、SET NULL:从父表删除和更新行，并设置子表中的外键列为NULL。如果使用该选项，必须保证子表列没有指定NOT NULL
3)、RESTRICT:拒绝对父表的删除或更新操作
4)、NO ACTION:标准SQL的关键字，在MYSQL中与RESTRICT相同
mysql> CREATE TABLE province(
-> id SMALLINT UNSIGNED PRIMARY KEY AUTO_INCREMENT,
-> pname VARCHAR(20) NOT NULL
-> );
Query OK, 0 rows affected (0.69 sec)
//外键类型需要与父表的相同
mysql> CREATE TABLE users(
-> id SMALLINT UNSIGNED PRIMARY KEY AUTO_INCREMENT,
-> username VARCHAR(10) NOT NULL,
-> pid SMALLINT ,FOREIGN KEY(pid) REFERENCES province(id)
-> );
ERROR 1215 (HY000): Cannot add foreign key constraint
mysql> CREATE TABLE users(
-> id SMALLINT UNSIGNED PRIMARY KEY AUTO_INCREMENT,
-> username VARCHAR(10) NOT NULL,
-> pid SMALLINT UNSIGNED ,FOREIGN KEY(pid) REFERENCES province(id)
-> );
Query OK, 0 rows affected (0.47 sec)
//CASCADE举例
mysql> CREATE TABLE users1(
-> id SMALLINT UNSIGNED PRIMARY KEY AUTO_INCREMENT,
-> username VARCHAR(10) NOT NULL,
-> pid SMALLINT UNSIGNED ,FOREIGN KEY(pid) REFERENCES province(id) ON DELETE CASCADE
-> );
Query OK, 0 rows affected (0.56 sec)
mysql> INSERT province(pname) VALUES('A');
Query OK, 1 row affected (0.14 sec)
mysql> INSERT province(pname) VALUES('B');
Query OK, 1 row affected (0.09 sec)
mysql> INSERT province(pname) VALUES('C');
Query OK, 1 row affected (0.09 sec)
mysql> SELECT *FROM province;
+----+-------+
| id | pname |
+----+-------+
| 1 | A |
| 2 | B |
| 3 | C |
+----+-------+
3 rows in set (0.06 sec)
mysql> INSERT users1(username,pid) VALUES('TOM',3);
Query OK, 1 row affected (0.09 sec)
mysql> INSERT users1(username,pid) VALUES('JOHN',2);
Query OK, 1 row affected (0.09 sec)
mysql> INSERT users1(username,pid) VALUES('HN',3);
Query OK, 1 row affected (0.10 sec)
mysql> SELECT *FROM users1;
+----+----------+------+
| id | username | pid |
+----+----------+------+
| 1 | TOM | 3 |
| 2 | JOHN | 2 |
| 3 | HN | 3 |
+----+----------+------+
3 rows in set (0.00 sec)
mysql> DELETE FROM province WHERE id = 3;
Query OK, 1 row affected (0.15 sec)
mysql> SELECT *FROM users1;
+----+----------+------+
| id | username | pid |
+----+----------+------+
| 2 | JOHN | 2 |
+----+----------+------+
1 row in set (0.00 sec)
3、表级约束和列级约束
列级约束：对一个数据列建立的约束
表级约束：对多个数据列建立的约束
不是所有的约束都存在列级和表级约束
4、修改数据表
1)、添加单列
ALTER TABLE table_name ADD [COLUMN] column_name column_definition
[FIRST | AFTER column_name]
FIRST：添加的列在最前方
AFTER column_name:添加的列在column_name后面
默认在最后一列
mysql> ALTER TABLE users1 ADD age TINYINT UNSIGNED NOT NULL DEFAULT 10;
Query OK, 0 rows affected (1.21 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> SHOW COLUMNS FROM users1;
+----------+----------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+----------+----------------------+------+-----+---------+----------------+
| id | smallint(5) unsigned | NO | PRI | NULL | auto_increment |
| username | varchar(10) | NO | | NULL | |
| pid | smallint(5) unsigned | YES | MUL | NULL | |
| age | tinyint(3) unsigned | NO | | 10 | |
+----------+----------------------+------+-----+---------+----------------+
4 rows in set (0.07 sec)
mysql> ALTER TABLE users1 ADD password VARCHAR(20) NOT NULL AFTER username;
Query OK, 0 rows affected (1.41 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> SHOW COLUMNS FROM users1;
+----------+----------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+----------+----------------------+------+-----+---------+----------------+
| id | smallint(5) unsigned | NO | PRI | NULL | auto_increment |
| username | varchar(10) | NO | | NULL | |
| password | varchar(20) | NO | | NULL | |
| pid | smallint(5) unsigned | YES | MUL | NULL | |
| age | tinyint(3) unsigned | NO | | 10 | |
+----------+----------------------+------+-----+---------+----------------+
5 rows in set (0.00 sec)
2)、添加多列
ALTER TABLE table_name ADD [COMLUM]
(column_name column_definition,...)
3)、删除列
ALTER TABLE table_name DROP column_name
ALTER TABLE table_name DROP column_name,...
mysql> ALTER TABLE users1 DROP username;
Query OK, 0 rows affected (1.27 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> SHOW COLUMNS FROM users1;
+----------+----------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+----------+----------------------+------+-----+---------+----------------+
| id | smallint(5) unsigned | NO | PRI | NULL | auto_increment |
| password | varchar(20) | NO | | NULL | |
| pid | smallint(5) unsigned | YES | MUL | NULL | |
| age | tinyint(3) unsigned | NO | | 10 | |
+----------+----------------------+------+-----+---------+----------------+
4 rows in set (0.00 sec)
mysql> ALTER TABLE users1 DROP password,DROP age;
Query OK, 0 rows affected (1.40 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> SHOW COLUMNS FROM users1;
+-------+----------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------+----------------------+------+-----+---------+----------------+
| id | smallint(5) unsigned | NO | PRI | NULL | auto_increment |
| pid | smallint(5) unsigned | YES | MUL | NULL | |
+-------+----------------------+------+-----+---------+----------------+
2 rows in set (0.00 sec)
4)、添加主键约束
ALTER TABLE table_name ADD [CONSTRAINT [symbol]] PRIMARY KEY
[index_type](index_col_name,...)
5)、添加唯一约束
ALTER TABLE table_name ADD [CONSTRAINT [symbol]] UNIQUE
[INDEX|KEY][index_name][index_type](index_col_name,...)
6)、添加外键约束
ALTER TABLE table_name ADD [CONSTRAINT [symbol]] FOREIGN KEY
[INDEX|KEY][index_name](index_col_name,...)
reference_definition
7)、添加/删除默认约束
ALTER TABLE table_name ALTER [COLUMN] col_name
{SET DEFAULT literal|DROP DEFAULT}
8)、删除主键约束
ALTER TABLE table_name DROP PRIMARY KEY;
9)、删除唯一约束
ALTER TABLE table_name DROP INDEX {INDEX|KEY}index_name;
10)、删除外键约束
ALTER TABLE table_name DROP FOREIGN KEY fk_symbol
11)、修改列定义
ALTER TABLE table_name MODIEY [COLUMN]old_col_name new_col_name
column_definition [FIRST|AFTER col_name]
12)、数据表更名
方法1：ALTER TABLE table_name RENAME [TO|AS] new_table_name
方法2：RENAME TABLE table_name TO new_table_name
九、记录的操作
1、插入记录
方法1：
INSERT [INTO] table_name [col_name,...] {VALUES|VALUE}({expr|DEFAULT},...),(...),...
mysql> CREATE TABLE users(
-> id SMALLINT UNSIGNED PRIMARY KEY AUTO_INCREMENT,
-> username VARCHAR(20) NOT NULL,
-> password VARCHAR(20) NOT NULL,
-> age TINYINT UNSIGNED NOT NULL DEFAULT 10,
-> sex BOOLEAN
-> );
Query OK, 0 rows affected (0.46 sec)
mysql> INSERT users VALUES(NULL,'Tom','123',20,1);
Query OK, 1 row affected (0.14 sec)
mysql> select *from users;
+----+----------+----------+-----+------+
| id | username | password | age | sex |
+----+----------+----------+-----+------+
| 1 | Tom | 123 | 20 | 1 |
+----+----------+----------+-----+------+
1 row in set (0.00 sec)
mysql> INSERT users VALUES(NULL,'John','123',19,1);
Query OK, 1 row affected (0.09 sec)
mysql> select *from users;
+----+----------+----------+-----+------+
| id | username | password | age | sex |
+----+----------+----------+-----+------+
| 1 | Tom | 123 | 20 | 1 |
| 2 | John | 123 | 19 | 1 |
+----+----------+----------+-----+------+
2 rows in set (0.00 sec)
mysql> INSERT users VALUES(NULL,'Tom','123',20,1);
Query OK, 1 row affected (0.04 sec)
mysql> select *from users;
+----+----------+----------+-----+------+
| id | username | password | age | sex |
+----+----------+----------+-----+------+
| 1 | Tom | 123 | 20 | 1 |
| 2 | John | 123 | 19 | 1 |
| 3 | Tom | 123 | 20 | 1 |
+----+----------+----------+-----+------+
3 rows in set (0.00 sec)
//使用默认值
mysql> INSERT users VALUES(NULL,'Tom','123',DEFAULT,1);
Query OK, 1 row affected (0.09 sec)
mysql> select *from users;
+----+----------+----------+-----+------+
| id | username | password | age | sex |
+----+----------+----------+-----+------+
| 1 | Tom | 123 | 20 | 1 |
| 2 | John | 123 | 19 | 1 |
| 3 | Tom | 123 | 20 | 1 |
| 4 | Tom | 123 | 10 | 1 |
+----+----------+----------+-----+------+
4 rows in set (0.00 sec)
//多行赋值
mysql> INSERT users VALUES(NULL,'Tim','123',20,1),(NULL,'Rose','123',20,1)
-> ;
Query OK, 2 rows affected (0.09 sec)
Records: 2 Duplicates: 0 Warnings: 0
mysql> select *from users;
+----+----------+----------+-----+------+
| id | username | password | age | sex |
+----+----------+----------+-----+------+
| 1 | Tom | 123 | 20 | 1 |
| 2 | John | 123 | 19 | 1 |
| 3 | Tom | 123 | 20 | 1 |
| 4 | Tom | 123 | 10 | 1 |
| 5 | Tim | 123 | 20 | 1 |
| 6 | Rose | 123 | 20 | 1 |
+----+----------+----------+-----+------+
6 rows in set (0.00 sec)
方法2(使用较少)：
INSERT [INTO] table_name SET col_name={expr|DEFAULT},...
说明：与第一种方式的区别在于，此方法可以使用子查询（SubQuery）
mysql> INSERT users SET username = 'Ben',password = '123';
Query OK, 1 row affected (0.06 sec)
mysql> select *from users;
+----+----------+----------+-----+------+
| id | username | password | age | sex |
+----+----------+----------+-----+------+
| 1 | Tom | 123 | 20 | 1 |
| 2 | John | 123 | 19 | 1 |
| 3 | Tom | 123 | 20 | 1 |
| 4 | Tom | 123 | 10 | 1 |
| 5 | Tim | 123 | 20 | 1 |
| 6 | Rose | 123 | 20 | 1 |
| 7 | Ben | 123 | 10 | NULL |
+----+----------+----------+-----+------+
7 rows in set (0.00 sec)
方法3：
INSERT [INTO] table_name[(col_name),...] SELECT ...
说明：此方法可以将查询结果插入到指定的数据表
2、更新记录
单表更新
UPDATE[LOW_PRIORITY][IGNORE]table_reference SET col_name1={expr1|DEFAULT}
[,col_name2={expr2|DEFAULT}]...[WHERE where_condition]
//省略条件，更新全部数据
mysql> UPDATE users set age = age + 5;
Query OK, 7 rows affected (0.12 sec)
Rows matched: 7 Changed: 7 Warnings: 0
mysql> select *from users;
+----+----------+----------+-----+------+
| id | username | password | age | sex |
+----+----------+----------+-----+------+
| 1 | Tom | 123 | 25 | 1 |
| 2 | John | 123 | 24 | 1 |
| 3 | Tom | 123 | 25 | 1 |
| 4 | Tom | 123 | 15 | 1 |
| 5 | Tim | 123 | 25 | 1 |
| 6 | Rose | 123 | 25 | 1 |
| 7 | Ben | 123 | 15 | NULL |
+----+----------+----------+-----+------+
7 rows in set (0.00 sec)
//多字段更新
mysql> UPDATE users set age = age - id,sex = 0;
Query OK, 7 rows affected (0.09 sec)
Rows matched: 7 Changed: 7 Warnings: 0
mysql> select *from users;
+----+----------+----------+-----+------+
| id | username | password | age | sex |
+----+----------+----------+-----+------+
| 1 | Tom | 123 | 24 | 0 |
| 2 | John | 123 | 22 | 0 |
| 3 | Tom | 123 | 22 | 0 |
| 4 | Tom | 123 | 11 | 0 |
| 5 | Tim | 123 | 20 | 0 |
| 6 | Rose | 123 | 19 | 0 |
| 7 | Ben | 123 | 8 | 0 |
+----+----------+----------+-----+------+
7 rows in set (0.00 sec)
//条件更新
mysql> UPDATE users set age = age + 10 WHERE id%2=0;
Query OK, 3 rows affected (0.09 sec)
Rows matched: 3 Changed: 3 Warnings: 0
mysql> select *from users;
+----+----------+----------+-----+------+
| id | username | password | age | sex |
+----+----------+----------+-----+------+
| 1 | Tom | 123 | 24 | 0 |
| 2 | John | 123 | 32 | 0 |
| 3 | Tom | 123 | 22 | 0 |
| 4 | Tom | 123 | 21 | 0 |
| 5 | Tim | 123 | 20 | 0 |
| 6 | Rose | 123 | 29 | 0 |
| 7 | Ben | 123 | 8 | 0 |
+----+----------+----------+-----+------+
7 rows in set (0.00 sec)
3、删除记录
单表：
DELETE FROM table_name [WHERE where_condition]
mysql> DELETE FROM users WHERE id = 6;
Query OK, 1 row affected (0.06 sec)
mysql> select *from users;
+----+----------+----------+-----+------+
| id | username | password | age | sex |
+----+----------+----------+-----+------+
| 1 | Tom | 123 | 24 | 0 |
| 2 | John | 123 | 32 | 0 |
| 3 | Tom | 123 | 22 | 0 |
| 4 | Tom | 123 | 21 | 0 |
| 5 | Tim | 123 | 20 | 0 |
| 7 | Ben | 123 | 8 | 0 |
+----+----------+----------+-----+------+
6 rows in set (0.00 sec)
4、查询表达式解析
查找记录
SELECT select_expr [,select_expr...]
[
FROM table_references
[WHERE where_condition]
[GROUP BY{col_name|position}[ASC|DESC],...]
[HAVING where_condition]
[ORDER BY{col_name|expr|position}[ASC|DESC],...]
[LIMIT{[offset,]row_count|row_count OFFSET offset}]
]
mysql> SELECT 3+5;
+-----+
| 3+5 |
+-----+
| 8 |
+-----+
1 row in set (0.00 sec)
mysql> SELECT username,id FROM users;
+----------+----+
| username | id |
+----------+----+
| Tom | 1 |
| John | 2 |
| Tom | 3 |
| Tom | 4 |
| Tim | 5 |
| Ben | 7 |
+----------+----+
6 rows in set (0.00 sec)
查询表达式
每一个表达式表示想要的一列，必须有至少一个
多列之间以英文逗号
星号（*）表示所有列。table_name.*可以表示命名表的所有列
查询表达式可以使用[AS]alias_name为其赋予别名
别名可用与GROUP BY,ORDER BY或HAVING子句
5、条件表达式
对记录进行过滤，如果没有指定WHERE子句，则显示所有记录。
在WHERE表达式中，可以使用MYSQL支持的函数或运算符
6、查询结果分组GROUP BY
[GROUP BY{col_name|position}[ASC|DESC],...]
mysql> SELECT sex FROM users GROUP BY sex;
+------+
| sex |
+------+
| 0 |
+------+
1 row in set (0.05 sec)
7、分组条件
[HAVING where_condition]
mysql> SELECT age FROM users GROUP BY age HAVING age >22;
+-----+
| age |
+-----+
| 24 |
| 32 |
+-----+
2 rows in set (0.00 sec)
十、子查询和连接
子查询是指在另一个查询语句中的SELECT子句。
例句：
SELECT * FROM t1 WHERE column1 = (SELECT column1 FROM t2);
其中，SELECT * FROM t1 ...称为Outer Query[外查询](或者Outer Statement),
SELECT column1 FROM t2 称为Sub Query[子查询]。
所以，我们说子查询是嵌套在外查询内部。而事实上它有可能在子查询内部再嵌套子查询。
子查询必须出现在圆括号之间。
1、使用比较运算符的子查询
运算符：=、>、<、<=、>=、<>、!=、<=>
语法结构：operand comparisor_operator subquery
mysql> SELECT AVG(goods_price) FROM tdb_goods;
+------------------+
| AVG(goods_price) |
+------------------+
| 5636.3636364 |
+------------------+
1 row in set (0.01 sec)
mysql> SELECT ROUND(AVG(goods_price),2) FROM tdb_goods;
+---------------------------+
| ROUND(AVG(goods_price),2) |
+---------------------------+
| 5636.36 |
+---------------------------+
1 row in set (0.00 sec)
mysql> SELECT goods_id,goods_name,goods_price FROM tdb_goods WHERE goods_price >=5636.36;
+----------+-----------------------------------------+-------------+
| goods_id | goods_name | goods_price |
+----------+-----------------------------------------+-------------+
| 3 | G150TH 15.6英寸游戏本 | 8499.000 |
| 7 | SVP13226SCB 13.3英寸触控超极本 | 7999.000 |
| 13 | iMac ME086CH/A 21.5英寸一体电脑 | 9188.000 |
| 17 | Mac Pro MD878CH/A 专业级台式电脑 | 28888.000 |
| 18 | HMZ-T3W 头戴显示设备 | 6999.000 |
| 20 | X3250 M4机架式服务器 2583i14 | 6888.000 |
| 21 | HMZ-T3W 头戴显示设备 | 6999.000 |
+----------+-----------------------------------------+-------------+
7 rows in set (0.00 sec)
mysql> SELECT goods_id,goods_name,goods_price FROM tdb_goods WHERE goods_price >=(SELECT ROUND(AVG(goods_price),2) FROM tdb_goods);
+----------+-----------------------------------------+-------------+
| goods_id | goods_name | goods_price |
+----------+-----------------------------------------+-------------+
| 3 | G150TH 15.6英寸游戏本 | 8499.000 |
| 7 | SVP13226SCB 13.3英寸触控超极本 | 7999.000 |
| 13 | iMac ME086CH/A 21.5英寸一体电脑 | 9188.000 |
| 17 | Mac Pro MD878CH/A 专业级台式电脑 | 28888.000 |
| 18 | HMZ-T3W 头戴显示设备 | 6999.000 |
| 20 | X3250 M4机架式服务器 2583i14 | 6888.000 |
| 21 | HMZ-T3W 头戴显示设备 | 6999.000 |
+----------+-----------------------------------------+-------------+
7 rows in set (0.00 sec)
2、用ANY\SOME\或ALL修饰的比较运算符
operand comparisor_operator ANY(subquery)
operand comparisor_operator SOME(subquery)
operand comparisor_operator ALL(subquery)
mysql> SELECT goods_id,goods_name,goods_price FROM tdb_goods WHERE goods_price >= ANY(SELECT ROUND(AVG(goods_price),2) FROM tdb_goods);
+----------+-----------------------------------------+-------------+
| goods_id | goods_name | goods_price |
+----------+-----------------------------------------+-------------+
| 3 | G150TH 15.6英寸游戏本 | 8499.000 |
| 7 | SVP13226SCB 13.3英寸触控超极本 | 7999.000 |
| 13 | iMac ME086CH/A 21.5英寸一体电脑 | 9188.000 |
| 17 | Mac Pro MD878CH/A 专业级台式电脑 | 28888.000 |
| 18 | HMZ-T3W 头戴显示设备 | 6999.000 |
| 20 | X3250 M4机架式服务器 2583i14 | 6888.000 |
| 21 | HMZ-T3W 头戴显示设备 | 6999.000 |
+----------+-----------------------------------------+-------------+
7 rows in set (0.00 sec)
mysql> SELECT goods_id,goods_name,goods_price FROM tdb_goods WHERE goods_price >= ALL(SELECT ROUND(AVG(goods_price),2) FROM tdb_goods);
+----------+-----------------------------------------+-------------+
| goods_id | goods_name | goods_price |
+----------+-----------------------------------------+-------------+
| 3 | G150TH 15.6英寸游戏本 | 8499.000 |
| 7 | SVP13226SCB 13.3英寸触控超极本 | 7999.000 |
| 13 | iMac ME086CH/A 21.5英寸一体电脑 | 9188.000 |
| 17 | Mac Pro MD878CH/A 专业级台式电脑 | 28888.000 |
| 18 | HMZ-T3W 头戴显示设备 | 6999.000 |
| 20 | X3250 M4机架式服务器 2583i14 | 6888.000 |
| 21 | HMZ-T3W 头戴显示设备 | 6999.000 |
+----------+-----------------------------------------+-------------+
7 rows in set (0.01 sec)
mysql> SELECT goods_id,goods_name,goods_price FROM tdb_goods WHERE goods_price >= SOME(SELECT ROUND(AVG(goods_price),2) FROM tdb_goods);
+----------+-----------------------------------------+-------------+
| goods_id | goods_name | goods_price |
+----------+-----------------------------------------+-------------+
| 3 | G150TH 15.6英寸游戏本 | 8499.000 |
| 7 | SVP13226SCB 13.3英寸触控超极本 | 7999.000 |
| 13 | iMac ME086CH/A 21.5英寸一体电脑 | 9188.000 |
| 17 | Mac Pro MD878CH/A 专业级台式电脑 | 28888.000 |
| 18 | HMZ-T3W 头戴显示设备 | 6999.000 |
| 20 | X3250 M4机架式服务器 2583i14 | 6888.000 |
| 21 | HMZ-T3W 头戴显示设备 | 6999.000 |
+----------+-----------------------------------------+-------------+
7 rows in set (0.00 sec)
3、INT EXISTS(少用)引发的子查询
operand comparisor_operator [NOT] IN(subquery)
4、使用INSERT ... SELECT插入记录
将查询结果写入数据表
INSERT [INTO] table_name[(col_name,...)] SELECT ...
例句：INSERT tdb_goods_cates(cate_name) SELECT goods_cate FROM GROUP BY goods_cate;
mysql> SELECT goods_cate FROM tdb_goods GROUP BY goods_cate;
+---------------------+
| goods_cate |
+---------------------+
| 台式机 |
| 平板电脑 |
| 服务器/工作站 |
| 游戏本 |
| 笔记本 |
| 笔记本配件 |
| 超级本 |
+---------------------+
7 rows in set (0.00 sec)
mysql> INSERT tdb_goods_cates (cate_name) SELECT goods_cate FROM tdb_goods GROUP BY goods_cate;
Query OK, 7 rows affected (0.10 sec)
Records: 7 Duplicates: 0 Warnings: 0
mysql> SELECT *FROM tdb_goods_cates;
+---------+---------------------+
| cate_id | cate_name |
+---------+---------------------+
| 1 | 台式机 |
| 2 | 平板电脑 |
| 3 | 服务器/工作站 |
| 4 | 游戏本 |
| 5 | 笔记本 |
| 6 | 笔记本配件 |
| 7 | 超级本 |
+---------+---------------------+
7 rows in set (0.00 sec)
5、多表更新
语法结构：tale_reference {[INNER|CROSS]JOIN|{LEFT|RIGHT}[OUTER]JOIN}
table_reference ON conditional_expr
INNER JOIN 内连接
在MYSQL中，JOIN,CROSS JOIN和INNER JOIN是等价的
LEFT[OUTER] JOIN左外连接
RIGHT[OUTER] JOIN右外连接
mysql> UPDATE tdb_goods INNER JOIN tdb_goods_cates ON goods_cate = cate_name SET goods_cate = cate_id;
Query OK, 22 rows affected (0.09 sec)
Rows matched: 22 Changed: 22 Warnings: 0
mysql> SELECT *FROM tdb_goods;
+----------+--------------------------------------------------------------------------------------+------------+------------+-------------+---------+------------+
| goods_id | goods_name | goods_cate | brand_name | goods_price | is_show | is_saleoff |
+----------+--------------------------------------------------------------------------------------+------------+------------+-------------+---------+------------+
| 1 | R510VC 15.6英寸笔记本 | 5 | 华硕 | 3399.000 | 1 | 0 |
| 2 | Y400N 14.0英寸笔记本电脑 | 5 | 联想 | 4899.000 | 1 | 0 |
| 3 | G150TH 15.6英寸游戏本 | 4 | 雷神 | 8499.000 | 1 | 0 |
| 4 | X550CC 15.6英寸笔记本 | 5 | 华硕 | 2799.000 | 1 | 0 |
| 5 | X240(20ALA0EYCD) 12.5英寸超极本 | 7 | 联想 | 4999.000 | 1 | 0 |
| 6 | U330P 13.3英寸超极本 | 7 | 联想 | 4299.000 | 1 | 0 |
| 7 | SVP13226SCB 13.3英寸触控超极本 | 7 | 索尼 | 7999.000 | 1 | 0 |
| 8 | iPad mini MD531CH/A 7.9英寸平板电脑 | 2 | 苹果 | 1998.000 | 1 | 0 |
| 9 | iPad Air MD788CH/A 9.7英寸平板电脑 （16G WiFi版） | 2 | 苹果 | 3388.000 | 1 | 0 |
| 10 | iPad mini ME279CH/A 配备 Retina 显示屏 7.9英寸平板电脑 （16G WiFi版） | 2 | 苹果 | 2788.000 | 1 | 0 |
| 11 | IdeaCentre C340 20英寸一体电脑 | 1 | 联想 | 3499.000 | 1 | 0 |
| 12 | Vostro 3800-R1206 台式电脑 | 1 | 戴尔 | 2899.000 | 1 | 0 |
| 13 | iMac ME086CH/A 21.5英寸一体电脑 | 1 | 苹果 | 9188.000 | 1 | 0 |
| 14 | AT7-7414LP 台式电脑 （i5-3450四核 4G 500G 2G独显 DVD 键鼠 Linux ） | 1 | 宏碁 | 3699.000 | 1 | 0 |
| 15 | Z220SFF F4F06PA工作站 | 3 | 惠普 | 4288.000 | 1 | 0 |
| 16 | PowerEdge T110 II服务器 | 3 | 戴尔 | 5388.000 | 1 | 0 |
| 17 | Mac Pro MD878CH/A 专业级台式电脑 | 3 | 苹果 | 28888.000 | 1 | 0 |
| 18 | HMZ-T3W 头戴显示设备 | 6 | 索尼 | 6999.000 | 1 | 0 |
| 19 | 商务双肩背包 | 6 | 索尼 | 99.000 | 1 | 0 |
| 20 | X3250 M4机架式服务器 2583i14 | 3 | IBM | 6888.000 | 1 | 0 |
| 21 | HMZ-T3W 头戴显示设备 | 6 | 索尼 | 6999.000 | 1 | 0 |
| 22 | 商务双肩背包 | 6 | 索尼 | 99.000 | 1 | 0 |
+----------+--------------------------------------------------------------------------------------+------------+------------+-------------+---------+------------+
22 rows in set (0.00 sec)
6、多表更新之一步到位
UPDATE table_references SET col_name1 = {expr1|DEFAULT}
[,col_name2 = {expr2|DEFAULT}]...
[WHERE where_condition]
创建数据表的同时将查询结果写入数据表
CREAT TABLE [IF NOT EXISTS] table_name
[(creat_definition,...)]
select_statement
mysql> SELECT brand_name FROM tdb_goods GROUP BY brand_name;
+------------+
| brand_name |
+------------+
| IBM |
| 华硕 |
| 宏碁 |
| 惠普 |
| 戴尔 |
| 索尼 |
| 联想 |
| 苹果 |
| 雷神 |
+------------+
9 rows in set (0.94 sec)
mysql> CREATE TABLE tdb_goods_brands(
-> brand_id SMALLINT UNSIGNED PRIMARY KEY AUTO_INCREMENT,
-> brand_name VARCHAR(40) NOT NULL
-> )
-> SELECT brand_name FROM tdb_goods GROUP BY brand_name;
Query OK, 9 rows affected (0.78 sec)
Records: 9 Duplicates: 0 Warnings: 0
mysql> show tables ;
+------------------+
| Tables_in_t1 |
+------------------+
| tdb_goods |
| tdb_goods_brands |
| tdb_goods_cates |
| tdb_goods_types |
| users |
+------------------+
5 rows in set (0.00 sec)
mysql> SELECT *FROM tdb_goods_brands;
+----------+------------+
| brand_id | brand_name |
+----------+------------+
| 1 | IBM |
| 2 | 华硕 |
| 3 | 宏碁 |
| 4 | 惠普 |
| 5 | 戴尔 |
| 6 | 索尼 |
| 7 | 联想 |
| 8 | 苹果 |
| 9 | 雷神 |
+----------+------------+
9 rows in set (0.00 sec)
//创建内连接
mysql> UPDATE tdb_goods AS g INNER JOIN tdb_goods_brands AS b ON g.brand_name =b.brand_name
-> SET g.brand_name = b.brand_id;
Query OK, 22 rows affected (0.16 sec)
Rows matched: 22 Changed: 22 Warnings: 0
mysql> SELECT *FROM tdb_goods_brands;
+----------+------------+
| brand_id | brand_name |
+----------+------------+
| 1 | IBM |
| 2 | 华硕 |
| 3 | 宏碁 |
| 4 | 惠普 |
| 5 | 戴尔 |
| 6 | 索尼 |
| 7 | 联想 |
| 8 | 苹果 |
| 9 | 雷神 |
+----------+------------+
9 rows in set (0.00 sec)
mysql> SELECT *FROM tdb_goods;
+----------+--------------------------------------------------------------------------------------+------------+------------+-------------+---------+------------+
| goods_id | goods_name | goods_cate | brand_name | goods_price | is_show | is_saleoff |
+----------+--------------------------------------------------------------------------------------+------------+------------+-------------+---------+------------+
| 1 | R510VC 15.6英寸笔记本 | 5 | 2 | 3399.000 | 1 | 0 |
| 2 | Y400N 14.0英寸笔记本电脑 | 5 | 7 | 4899.000 | 1 | 0 |
| 3 | G150TH 15.6英寸游戏本 | 4 | 9 | 8499.000 | 1 | 0 |
| 4 | X550CC 15.6英寸笔记本 | 5 | 2 | 2799.000 | 1 | 0 |
| 5 | X240(20ALA0EYCD) 12.5英寸超极本 | 7 | 7 | 4999.000 | 1 | 0 |
| 6 | U330P 13.3英寸超极本 | 7 | 7 | 4299.000 | 1 | 0 |
| 7 | SVP13226SCB 13.3英寸触控超极本 | 7 | 6 | 7999.000 | 1 | 0 |
| 8 | iPad mini MD531CH/A 7.9英寸平板电脑 | 2 | 8 | 1998.000 | 1 | 0 |
| 9 | iPad Air MD788CH/A 9.7英寸平板电脑 （16G WiFi版） | 2 | 8 | 3388.000 | 1 | 0 |
| 10 | iPad mini ME279CH/A 配备 Retina 显示屏 7.9英寸平板电脑 （16G WiFi版） | 2 | 8 | 2788.000 | 1 | 0 |
| 11 | IdeaCentre C340 20英寸一体电脑 | 1 | 7 | 3499.000 | 1 | 0 |
| 12 | Vostro 3800-R1206 台式电脑 | 1 | 5 | 2899.000 | 1 | 0 |
| 13 | iMac ME086CH/A 21.5英寸一体电脑 | 1 | 8 | 9188.000 | 1 | 0 |
| 14 | AT7-7414LP 台式电脑 （i5-3450四核 4G 500G 2G独显 DVD 键鼠 Linux ） | 1 | 3 | 3699.000 | 1 | 0 |
| 15 | Z220SFF F4F06PA工作站 | 3 | 4 | 4288.000 | 1 | 0 |
| 16 | PowerEdge T110 II服务器 | 3 | 5 | 5388.000 | 1 | 0 |
| 17 | Mac Pro MD878CH/A 专业级台式电脑 | 3 | 8 | 28888.000 | 1 | 0 |
| 18 | HMZ-T3W 头戴显示设备 | 6 | 6 | 6999.000 | 1 | 0 |
| 19 | 商务双肩背包 | 6 | 6 | 99.000 | 1 | 0 |
| 20 | X3250 M4机架式服务器 2583i14 | 3 | 1 | 6888.000 | 1 | 0 |
| 21 | HMZ-T3W 头戴显示设备 | 6 | 6 | 6999.000 | 1 | 0 |
| 22 | 商务双肩背包 | 6 | 6 | 99.000 | 1 | 0 |
+----------+--------------------------------------------------------------------------------------+------------+------------+-------------+---------+------------+
22 rows in set (0.00 sec)
//改变字段的数据类型
mysql> ALTER TABLE tdb_goods
-> CHANGE goods_cate cate_id SMALLINT UNSIGNED NOT NULL,
-> CHANGE brand_name brand_id SMALLINT UNSIGNED NOT NULL;
Query OK, 22 rows affected (1.12 sec)
Records: 22 Duplicates: 0 Warnings: 0
//查看表的定义
mysql> SHOW COLUMNS FROM tdb_goods;
+-------------+------------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------------+------------------------+------+-----+---------+----------------+
| goods_id | smallint(5) unsigned | NO | PRI | NULL | auto_increment |
| goods_name | varchar(150) | NO | | NULL | |
| cate_id | smallint(5) unsigned | NO | | NULL | |
| brand_id | smallint(5) unsigned | NO | | NULL | |
| goods_price | decimal(15,3) unsigned | NO | | 0.000 | |
| is_show | tinyint(1) | NO | | 1 | |
| is_saleoff | tinyint(1) | NO | | 0 | |
+-------------+------------------------+------+-----+---------+----------------+
7 rows in set (0.00 sec)
7、连接
语法结构：table_reference
{[INNER|CROSS]JOIN|{LEFT|RIGHT}[OUTER]JOIN}
table_reference ON conditional_expr
数据表参照
table_reference
table_name [[AS]alias]|table_subquery [AS] alias
数据表可以使用table_name AS alias_name或者table_name alias_name赋予别名
table_subquery可以作为子查询使用在FROM子句中，这样的查询不许为其赋予别名
MYSQL在SELECT语句、多表更新、多表删除语句中支持JOIN操作
8、连接类型
INNER JOIN 内连接
在MYSQL中，JOIN,CROSS JOIN和INNER JOIN是等价的
LEFT[OUTER] JOIN左外连接
RIGHT[OUTER] JOIN右外连接
使用ON关键字来设定连接条件，也可以使用WHERE来代替
通常使用ON关键字来设定连接条件，使用WHERE关键字进行结果集记录的过滤
mysql> SELECT goods_id,goods_name,cate_name FROM tdb_goods INNER JOIN tdb_goods_cates ON tdb_goods.cate_id = tdb_goods_cates.cate_id;
+----------+--------------------------------------------------------------------------------------+---------------------+
| goods_id | goods_name | cate_name |
+----------+--------------------------------------------------------------------------------------+---------------------+
| 1 | R510VC 15.6英寸笔记本 | 笔记本 |
| 2 | Y400N 14.0英寸笔记本电脑 | 笔记本 |
| 3 | G150TH 15.6英寸游戏本 | 游戏本 |
| 4 | X550CC 15.6英寸笔记本 | 笔记本 |
| 5 | X240(20ALA0EYCD) 12.5英寸超极本 | 超级本 |
| 6 | U330P 13.3英寸超极本 | 超级本 |
| 7 | SVP13226SCB 13.3英寸触控超极本 | 超级本 |
| 8 | iPad mini MD531CH/A 7.9英寸平板电脑 | 平板电脑 |
| 9 | iPad Air MD788CH/A 9.7英寸平板电脑 （16G WiFi版） | 平板电脑 |
| 10 | 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 |
| 11 | IdeaCentre C340 20英寸一体电脑 | 台式机 |
| 12 | Vostro 3800-R1206 台式电脑 | 台式机 |
| 13 | iMac ME086CH/A 21.5英寸一体电脑 | 台式机 |
| 14 | AT7-7414LP 台式电脑 （i5-3450四核 4G 500G 2G独显 DVD 键鼠 Linux ） | 台式机 |
| 15 | Z220SFF F4F06PA工作站 | 服务器/工作站 |
| 16 | PowerEdge T110 II服务器 | 服务器/工作站 |
| 17 | Mac Pro MD878CH/A 专业级台式电脑 | 服务器/工作站 |
| 18 | HMZ-T3W 头戴显示设备 | 笔记本配件 |
| 19 | 商务双肩背包 | 笔记本配件 |
| 20 | X3250 M4机架式服务器 2583i14 | 服务器/工作站 |
| 21 | HMZ-T3W 头戴显示设备 | 笔记本配件 |
| 22 | 商务双肩背包 | 笔记本配件 |
+----------+--------------------------------------------------------------------------------------+---------------------+
22 rows in set (0.07 sec)
十一、运算符和函数
1、字符函数
mysql> SELECT CONCAT('t1','-mysql');
+-----------------------+
| CONCAT('t1','-mysql') |
+-----------------------+
| t1-mysql |
+-----------------------+
1 row in set (0.09 sec)
mysql> SELECT CONCAT_ws('|','A','B','C');
+----------------------------+
| CONCAT_ws('|','A','B','C') |
+----------------------------+
| A|B|C |
+----------------------------+
1 row in set (0.06 sec)
mysql> SELECT FORMAT(12560.12,2);
+--------------------+
| FORMAT(12560.12,2) |
+--------------------+
| 12,560.12 |
+--------------------+
1 row in set (0.09 sec)
mysql> SELECT FORMAT(12560.12,1);
+--------------------+
| FORMAT(12560.12,1) |
+--------------------+
| 12,560.1 |
+--------------------+
1 row in set (0.00 sec)
mysql> SELECT FORMAT(12560.12,0);
+--------------------+
| FORMAT(12560.12,0) |
+--------------------+
| 12,560 |
+--------------------+
1 row in set (0.00 sec)
mysql> SELECT LOWER('MYSQl');
+----------------+
| LOWER('MYSQl') |
+----------------+
| mysql |
+----------------+
1 row in set (0.00 sec)
mysql> SELECT UPPER('mysQl');
+----------------+
| UPPER('mysQl') |
+----------------+
| MYSQL |
+----------------+
1 row in set (0.00 sec)
mysql> SELECT LEFT('MYSQL',2);
+-----------------+
| LEFT('MYSQL',2) |
+-----------------+
| MY |
+-----------------+
1 row in set (0.08 sec)
mysql> SELECT LOWER(LEFT('MYSQL',2));
+------------------------+
| LOWER(LEFT('MYSQL',2)) |
+------------------------+
| my |
+------------------------+
1 row in set (0.00 sec)
mysql> SELECT LOWER(RIGHT('MYSQL',3));
+-------------------------+
| LOWER(RIGHT('MYSQL',3)) |
+-------------------------+
| sql |
+-------------------------+
1 row in set (0.00 sec)
mysql> SELECT LENGTH('MY SQL');
+------------------+
| LENGTH('MY SQL') |
+------------------+
| 6 |
+------------------+
1 row in set (0.08 sec)
mysql> SELECT LTRIM(' MY SQL');
+------------------+
| LTRIM(' MY SQL') |
+------------------+
| MY SQL |
+------------------+
1 row in set (0.05 sec)
mysql> SELECT RTRIM(' MY SQL');
+------------------+
| RTRIM(' MY SQL') |
+------------------+
| MY SQL |
+------------------+
1 row in set (0.00 sec)
mysql> SELECT LENGTH(LTRIM(' MY SQL'));
+--------------------------+
| LENGTH(LTRIM(' MY SQL')) |
+--------------------------+
| 6 |
+--------------------------+
1 row in set (0.00 sec)
mysql> SELECT LENGTH(' MY SQL');
+-------------------+
| LENGTH(' MY SQL') |
+-------------------+
| 7 |
+-------------------+
1 row in set (0.00 sec)
mysql> SELECT SUBSTRING('MYSQL',1,2);
+------------------------+
| SUBSTRING('MYSQL',1,2) |
+------------------------+
| MY |
+------------------------+
1 row in set (0.00 sec)
mysql> SELECT 'MYSQL' LIKE 'M%';
+-------------------+
| 'MYSQL' LIKE 'M%' |
+-------------------+
| 1 |
+-------------------+
1 row in set (0.00 sec)
2、数值运算符与函数
mysql> SELECT 3+4;
+-----+
| 3+4 |
+-----+
| 7 |
+-----+
1 row in set (0.07 sec)
mysql> SELECT CEIL(4.01);
+------------+
| CEIL(4.01) |
+------------+
| 5 |
+------------+
1 row in set (0.06 sec)
mysql> SELECT FLOOR(4.01);
+-------------+
| FLOOR(4.01) |
+-------------+
| 4 |
+-------------+
1 row in set (0.00 sec)
mysql> SELECT 3/4;
+--------+
| 3/4 |
+--------+
| 0.7500 |
+--------+
1 row in set (0.06 sec)
mysql> SELECT 3 DIV 4;
+---------+
| 3 DIV 4 |
+---------+
| 0 |
+---------+
1 row in set (0.00 sec)
mysql> SELECT 3 % 4;
+-------+
| 3 % 4 |
+-------+
| 3 |
+-------+
1 row in set (0.00 sec)
mysql> SELECT 3 MOD 4;
+---------+
| 3 MOD 4 |
+---------+
| 3 |
+---------+
1 row in set (0.00 sec)
mysql> SELECT POWER(2,3);
+------------+
| POWER(2,3) |
+------------+
| 8 |
+------------+
1 row in set (0.07 sec)
mysql> SELECT ROUND(12123.311231,2)
-> ;
+-----------------------+
| ROUND(12123.311231,2) |
+-----------------------+
| 12123.31 |
+-----------------------+
1 row in set (0.07 sec)
mysql> SELECT TRUNCATE(12123.311231,2);
+--------------------------+
| TRUNCATE(12123.311231,2) |
+--------------------------+
| 12123.31 |
+--------------------------+
1 row in set (0.00 sec)
mysql> SELECT TRUNCATE(12123.1231,2);
+------------------------+
| TRUNCATE(12123.1231,2) |
+------------------------+
| 12123.12 |
+------------------------+
1 row in set (0.00 sec)
3、比较运算符与函数
mysql> SELECT 15 between 1 and 22;
+---------------------+
| 15 between 1 and 22 |
+---------------------+
| 1 |
+---------------------+
1 row in set (0.07 sec)
mysql> SELECT 15 not between 1 and 22;
+-------------------------+
| 15 not between 1 and 22 |
+-------------------------+
| 0 |
+-------------------------+
1 row in set (0.00 sec)
mysql> SELECT 10 IN (5,10,12,3);
+-------------------+
| 10 IN (5,10,12,3) |
+-------------------+
| 1 |
+-------------------+
1 row in set (0.07 sec)
mysql> SELECT NULL IS NULL;
+--------------+
| NULL IS NULL |
+--------------+
| 1 |
+--------------+
1 row in set (0.06 sec)
mysql> SELECT 0 IS NULL;
+-----------+
| 0 IS NULL |
+-----------+
| 0 |
+-----------+
1 row in set (0.00 sec)
4、日期时间函数
mysql> SELECT NOW();
+---------------------+
| NOW() |
+---------------------+
| 2018-10-01 16:28:53 |
+---------------------+
1 row in set (0.08 sec)
mysql> SELECT CURDATE();
+------------+
| CURDATE() |
+------------+
| 2018-10-01 |
+------------+
1 row in set (0.01 sec)
mysql> SELECT CURTIME();
+-----------+
| CURTIME() |
+-----------+
| 16:29:19 |
+-----------+
1 row in set (0.00 sec)
mysql> SELECT DATE_ADD('2018-10-01',INTERVAL 300 DAY);
+-----------------------------------------+
| DATE_ADD('2018-10-01',INTERVAL 300 DAY) |
+-----------------------------------------+
| 2019-07-28 |
+-----------------------------------------+
1 row in set (0.07 sec)
mysql> SELECT DATE_ADD('2018-10-01',INTERVAL -300 DAY);
+------------------------------------------+
| DATE_ADD('2018-10-01',INTERVAL -300 DAY) |
+------------------------------------------+
| 2017-12-05 |
+------------------------------------------+
1 row in set (0.01 sec)
mysql> SELECT DATE_ADD('2018-10-01',INTERVAL 3 WEEK);
+----------------------------------------+
| DATE_ADD('2018-10-01',INTERVAL 3 WEEK) |
+----------------------------------------+
| 2018-10-22 |
+----------------------------------------+
1 row in set (0.00 sec)
mysql> SELECT DATEDIFF('2017-06-09','2018-10-01');
+-------------------------------------+
| DATEDIFF('2017-06-09','2018-10-01') |
+-------------------------------------+
| -479 |
+-------------------------------------+
1 row in set (0.07 sec)
mysql> SELECT DATE_FORMAT('2018-10-01','%m/%d/%Y');
+--------------------------------------+
| DATE_FORMAT('2018-10-01','%m/%d/%Y') |
+--------------------------------------+
| 10/01/2018 |
+--------------------------------------+
1 row in set (0.00 sec)
5、信息函数
mysql> SELECT CONNECTION_ID();
+-----------------+
| CONNECTION_ID() |
+-----------------+
| 33 |
+-----------------+
1 row in set (0.00 sec)
mysql> SELECT DATABASE();
+------------+
| DATABASE() |
+------------+
| t1 |
+------------+
1 row in set (0.00 sec)
mysql> SELECT USER();
+----------------+
| USER() |
+----------------+
| root@localhost |
+----------------+
1 row in set (0.00 sec)
mysql> SELECT VERSION();
+-----------+
| VERSION() |
+-----------+
| 5.7.22 |
+-----------+
1 row in set (0.05 sec)
6、聚合函数
mysql> select *from tdb_goods;
+----------+--------------------------------------------------------------------------------------+---------+----------+-------------+---------+------------+
| goods_id | goods_name | cate_id | brand_id | goods_price | is_show | is_saleoff |
+----------+--------------------------------------------------------------------------------------+---------+----------+-------------+---------+------------+
| 1 | R510VC 15.6英寸笔记本 | 5 | 2 | 3399.000 | 1 | 0 |
| 2 | Y400N 14.0英寸笔记本电脑 | 5 | 7 | 4899.000 | 1 | 0 |
| 3 | G150TH 15.6英寸游戏本 | 4 | 9 | 8499.000 | 1 | 0 |
| 4 | X550CC 15.6英寸笔记本 | 5 | 2 | 2799.000 | 1 | 0 |
| 5 | X240(20ALA0EYCD) 12.5英寸超极本 | 7 | 7 | 4999.000 | 1 | 0 |
| 6 | U330P 13.3英寸超极本 | 7 | 7 | 4299.000 | 1 | 0 |
| 7 | SVP13226SCB 13.3英寸触控超极本 | 7 | 6 | 7999.000 | 1 | 0 |
| 8 | iPad mini MD531CH/A 7.9英寸平板电脑 | 2 | 8 | 1998.000 | 1 | 0 |
| 9 | iPad Air MD788CH/A 9.7英寸平板电脑 （16G WiFi版） | 2 | 8 | 3388.000 | 1 | 0 |
| 10 | iPad mini ME279CH/A 配备 Retina 显示屏 7.9英寸平板电脑 （16G WiFi版） | 2 | 8 | 2788.000 | 1 | 0 |
| 11 | IdeaCentre C340 20英寸一体电脑 | 1 | 7 | 3499.000 | 1 | 0 |
| 12 | Vostro 3800-R1206 台式电脑 | 1 | 5 | 2899.000 | 1 | 0 |
| 13 | iMac ME086CH/A 21.5英寸一体电脑 | 1 | 8 | 9188.000 | 1 | 0 |
| 14 | AT7-7414LP 台式电脑 （i5-3450四核 4G 500G 2G独显 DVD 键鼠 Linux ） | 1 | 3 | 3699.000 | 1 | 0 |
| 15 | Z220SFF F4F06PA工作站 | 3 | 4 | 4288.000 | 1 | 0 |
| 16 | PowerEdge T110 II服务器 | 3 | 5 | 5388.000 | 1 | 0 |
| 17 | Mac Pro MD878CH/A 专业级台式电脑 | 3 | 8 | 28888.000 | 1 | 0 |
| 18 | HMZ-T3W 头戴显示设备 | 6 | 6 | 6999.000 | 1 | 0 |
| 19 | 商务双肩背包 | 6 | 6 | 99.000 | 1 | 0 |
| 20 | X3250 M4机架式服务器 2583i14 | 3 | 1 | 6888.000 | 1 | 0 |
| 21 | HMZ-T3W 头戴显示设备 | 6 | 6 | 6999.000 | 1 | 0 |
| 22 | 商务双肩背包 | 6 | 6 | 99.000 | 1 | 0 |
| 23 | LaserJet Pro P1606dn 黑白激光打印机 | 12 | 4 | 1849.000 | 1 | 0 |
+----------+--------------------------------------------------------------------------------------+---------+----------+-------------+---------+------------+
23 rows in set (0.00 sec)
mysql> SELECT AVG(goods_price) FROM tdb_goods;
+------------------+
| AVG(goods_price) |
+------------------+
| 5471.6956522 |
+------------------+
1 row in set (0.22 sec)
mysql> SELECT COUNT(goods_id) FROM tdb_goods;
+-----------------+
| COUNT(goods_id) |
+-----------------+
| 23 |
+-----------------+
1 row in set (0.06 sec)
mysql> SELECT MIN(goods_price) FROM tdb_goods;
+------------------+
| MIN(goods_price) |
+------------------+
| 99.000 |
+------------------+
1 row in set (0.04 sec)
mysql> SELECT MAX(goods_price) FROM tdb_goods;
+------------------+
| MAX(goods_price) |
+------------------+
| 28888.000 |
+------------------+
1 row in set (0.00 sec)
mysql> SELECT SUM(goods_price) FROM tdb_goods;
+------------------+
| SUM(goods_price) |
+------------------+
| 125849.000 |
+------------------+
1 row in set (0.00 sec)
7、加密函数
MD5(); 信息摘要算法
PASSWORD(); 密码算法
mysql> SELECT MD5('admin');
+----------------------------------+
| MD5('admin') |
+----------------------------------+
| 21232f297a57a5a743894a0e4a801fc3 |
+----------------------------------+
1 row in set (0.00 sec)
mysql> SELECT PASSWORD('admin');
+-------------------------------------------+
| PASSWORD('admin') |
+-------------------------------------------+
| *4ACFE3202A5FF5CF467898FC58AAB1D615029441 |
+-------------------------------------------+
1 row in set, 1 warning (0.07 sec)
//修改密码
SET PASSWORD = PASSWORD('123456');8、自定义函数
自定义函数（UDF）
用户自定义函数（user-defined function,UDF）是一种MYSQL扩展的途径，用法和内置函数相同
函数可以返回任意的数据类型
创建自定义函数
CREAT FUNCTION function_name RETURNS
{STRING|INTEGER|REAL|DECIMAL}
routine_body
函数体：
函数体由合法的SQL语句组成
函数体可以是简单的SELECT或者INSERT语句
函数体如果未复合结构则使用BEGIN...END语句
符合结构可以包含声明，循环，控制结构
创建不带参的自定义函数
mysql> CREATE FUNCTION MYNOW() RETURNS VARCHAR(30)
-> RETURN DATE_FORMAT(NOW(),'%Y年%m月%d日 %H时%i分%s秒');
Query OK, 0 rows affected (0.04 sec)
mysql> SELECT MYNOW();
+-----------------------------------+
| MYNOW() |
+-----------------------------------+
| 2018年10月01日 18时51分43秒 |
+-----------------------------------+
1 row in set (0.00 sec)
创建带有参数的自定义函数
mysql> CREATE FUNCTION F2(num1 SMALLINT UNSIGNED,num2 SMALLINT UNSIGNED)
-> RETURNS FLOAT(10,2) UNSIGNED
-> RETURN (num1+num2)/2;
Query OK, 0 rows affected (0.00 sec)
mysql> SELECT F2(10,15);
+-----------+
| F2(10,15) |
+-----------+
| 12.50 |
+-----------+
1 row in set (0.06 sec)
创建具有复合结构函数体的自定义函数
必须包含在begin。。。end之间
删除自定义函数
DROP FUNCTION [IF EXISTS] function_name
十二、存储
1、存储过程简介
存储过程
SQL命令--》 MYSQL引擎--》分析 语法正确--》可识别命令
执行--》执行结果 返回--》客户端
存储过程是SQL语句和控制语句的预编译集合，以一个名称存储并作为单元处理
优点：
增强SQL语句的功能和灵活性
实现较快的执行速度
减少了网络流量
2、创建存储过程
CREAT
[DEFINER = {user|CURRENT_USER}]
PROCEDURE sp_name([proc_parameter[,...]])
[characteristic...]routine_body
proc_parameter:
[IN|OUT|INOUT]param_name type
参数：
IN,表示该参数的值必须在调用村塾过程时指定
OUT,表示该参数的值可以被存储过程改变，并且可以返回
INOUT,表示该参数的调用时指定，并且可以被改变和返回
过程体：
过程体由合法的SQL语句组成
过程体可以是任意SQL语句
过程体如果为复合结构则使用BEGIN...END语句
复合结构可以包含声明，循环，控制结构
3、调用存储过程：
CALL sp_name([parameter[,...]])
CALL sp_name[()]
4、删除存储过程：
DROP PROCEDURE [IF EXISTS]sp_name
mysql> DROP PROCEDURE removeUserById;
Query OK, 0 rows affected (0.04 sec)
5、创建不带参的存储过程
mysql> CREATE PROCEDURE sp1() SELECT VERSION();
Query OK, 0 rows affected (0.00 sec)
mysql> CALL sp1;
+-----------+
| VERSION() |
+-----------+
| 5.7.22 |
+-----------+
1 row in set (0.00 sec)
Query OK, 0 rows affected (0.00 sec)
6、创建带IN类型参的存储过程
mysql> SELECT *FROM users;
+----+----------+----------+-----+------+
| id | username | password | age | sex |
+----+----------+----------+-----+------+
| 1 | Tom | 123 | 24 | 0 |
| 2 | John | 123 | 32 | 0 |
| 3 | Tom | 123 | 22 | 0 |
| 4 | Tom | 123 | 21 | 0 |
| 5 | Tim | 123 | 20 | 0 |
| 7 | Ben | 123 | 8 | 0 |
+----+----------+----------+-----+------+
6 rows in set (0.08 sec)
mysql> DELIMITER //
mysql> CREATE PROCEDURE removeUserById (IN p_id INT UNSIGNED)
-> BEGIN
-> DELETE FROM users WHERE id = p_id;
-> END
-> //
Query OK, 0 rows affected (0.01 sec)
mysql> DELIMITER ;
mysql> CALL removeUserById(7);
Query OK, 1 row affected (0.09 sec)
mysql> SELECT *FROM users;
+----+----------+----------+-----+------+
| id | username | password | age | sex |
+----+----------+----------+-----+------+
| 1 | Tom | 123 | 24 | 0 |
| 2 | John | 123 | 32 | 0 |
| 3 | Tom | 123 | 22 | 0 |
| 4 | Tom | 123 | 21 | 0 |
| 5 | Tim | 123 | 20 | 0 |
+----+----------+----------+-----+------+
5 rows in set (0.00 sec)
7、创建带有IN和OUT类型参数的存储过程
mysql> SELECT *FROM users;
+----+----------+----------+-----+------+
| id | username | password | age | sex |
+----+----------+----------+-----+------+
| 1 | Tom | 123 | 24 | 0 |
| 2 | John | 123 | 32 | 0 |
| 3 | Tom | 123 | 22 | 0 |
| 4 | Tom | 123 | 21 | 0 |
| 5 | Tim | 123 | 20 | 0 |
+----+----------+----------+-----+------+
5 rows in set (0.14 sec)
//结束符修改为//
mysql> DELIMITER //
mysql> CREATE PROCEDURE removeUserAndReturnUserNum(IN p_id INT UNSIGNED,OUT userName INT UNSIGNED)
-> BEGIN
-> DELETE FROM users WHERE id = p_id;
-> SELECT count(id) FROM users INTO userNum;
-> end;
-> //
Query OK, 0 rows affected (0.13 sec)
//结束符修改为；
mysql> DELIMITER ;
mysql> SELECT COUNT(id) FROM users;
+-----------+
| COUNT(id) |
+-----------+
| 5 |
+-----------+
1 row in set (0.00 sec)
//删除ID为5的用户返回用户总数给用户变量@nums
mysql> CALL removeUserAndReturnUserNum(5,@nums);
Query OK, 1 row affected (0.12 sec)
mysql> SELECT *FROM users;
+----+----------+----------+-----+------+
| id | username | password | age | sex |
+----+----------+----------+-----+------+
| 1 | Tom | 123 | 24 | 0 |
| 2 | John | 123 | 32 | 0 |
| 3 | Tom | 123 | 22 | 0 |
| 4 | Tom | 123 | 21 | 0 |
+----+----------+----------+-----+------+
4 rows in set (0.00 sec)
mysql> SELECT @nums;
+-------+
| @nums |
+-------+
| 4 |
+-------+
1 row in set (0.00 sec)
8、创建带有多个OUT类型参数的存储过程
mysql> DELIMITER //
mysql> CREATE PROCEDURE removeUserByAgeAndReturnInfors(IN p_age SMALLINT UNSIGNED,OUT deleteUser SMALLINT UNSIGNED,OUT userCounts SMALLINT UNSIGNED)
-> BEGIN
-> DELETE FROM users WHERE age = p_age;
-> SELECT COUNT(id) FROM users INTO userCounts;
-> SELECT ROW_COUNT() INTO deleteUser;
-> END//
Query OK, 0 rows affected (0.00 sec)
mysql> DELIMITER ;
mysql> CALL removeUserByAgeAndReturnInfors(22,@a,@b);
Query OK, 1 row affected (0.00 sec)
mysql> SELECT @a,@b;
+------+------+
| @a | @b |
+------+------+
| 1 | 3 |
+------+------+
1 row in set (0.00 sec)
mysql> SELECT *FROM users;
+----+----------+----------+-----+------+
| id | username | password | age | sex |
+----+----------+----------+-----+------+
| 1 | Tom | 123 | 24 | 0 |
| 2 | John | 123 | 32 | 0 |
| 4 | Tom | 123 | 21 | 0 |
+----+----------+----------+-----+------+
3 rows in set (0.00 sec)
9、存储过程与自定义函数的区别
存储过程实现的功能要复杂一些；函数的针对性更强
存储过程可以返回多个值；函数只能有一个返回值
存储过程一般独立来执行；函数可以作为其他SQL语句的组成部分来出现
10、修改存储过程
ALTER PROCEDURE sp_name[characteristic...]
COMMENT 'string'
|{CONTAINS SQL|NO SQL|READS SQL DATA|MODIDIES SQL DATA}
|SQL SECURITY{DEFINER|INVOKER}
十三、存储引擎
1、存储引擎简介
MYSQL 可以将数据以不同的技术存储在文件（内存）中，这种技术称为存储引擎
每一种存储引擎使用不同的存储机制、索引技巧、锁定水平，最终提供广泛且不同的功能
MYSQL支持的存储引擎
MyISAM
InnoDB
Memory
CSV
Archive
2、相关知识点
并发控制：当多个连接对记录进行修改是保证数据的一致性和完整性
解决：锁
共享锁（读锁）：在同一时间段，多用户可以读取同一资源，读取过程中数据不会发生任何变化
排他锁（写锁）：在任何时候只能有一个用户写入资源，当进行写锁时会阻塞或者写锁操作
锁颗粒
表锁：一种开销最小的策略锁
行锁：一种开销最大的策略锁，支持最大并发
事务
事务用于保证数据库的完整性
事务的特性(ACID)
原子性（Atomicity）
一致性（Consistency）
隔离性（Isolation）
持久性（Durability）
外键
索引
是对数据表中一列或者多列的值进行排序的一种结构
分类：普通索引、唯一索引、全文索引、btree索引、hash索引
3、修改存储引擎方法
1)、通过修改MYSQL配置文件
-default-storage-engine = engine
2)、通过创建数据表命令实现
-CREATE TABLE table_name(
...
...
)ENGINE = engine;
3)、通过修改数据表命令实现
-ALTER TABLE table_name ENGINE [=] engine_name;