MySQL学习笔记-01-介绍、安装、数据库的创建、表的基本操作
文章目录
- MySQL介绍
- MySQL安装
-
- 1. exe
- 2. 免安装的方式
- MySQL环境的验证
- MySQL数据库的操作
-
- 数据库的操作
- 表的操作
-
- 表的创建
- 表的赋值
- 数据的基本操作
-
- 数据的插入
- 删除数据
- 修改数据
- 数据查询
- 运算符
-
- 去除重复
- 算数运算(+-*/)
- 比较运算
- 特殊的比较运算符
MySQL介绍
略
MySQL安装
1. exe
2. 免安装的方式
-
解压压缩包
mysql-5.7.18-winx64
“D:\Program Files\mysql-5.7.18-winx64”
- 启动服务(不需要操作)
- 注册成系统服务(开机启动)
- 管理员身份打开命令行
- 切换目录
C:\Windows\system32>d:
D:\>cd D:\Program Files\mysql-5.7.18-winx64\bin
D:\Program Files\mysql-5.7.18-winx64\bin>
- 注册系统服务
C:\Windows\system32>d:
D:\>cd D:\Program Files\mysql-5.7.18-winx64\bin
D:\Program Files\mysql-5.7.18-winx64\bin>mysqld --install
Service successfully installed.
D:\Program Files\mysql-5.7.18-winx64\bin>
-
验证系统服务是否安装成功
window徽标+R 运行
services.msc
- 启动mysql服务
MySQL环境的验证
打开cmd，切换到D:\Program Files\mysql-5.7.18-winx64\bin
- 连接数据库
D:\Program Files\mysql-5.7.18-winx64\bin>mysql -uroot -proot
mysql: [Warning] Using a password on the command line interface can be insecur
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 3
Server version: 5.7.18 MySQL Community Server (GPL)
Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql>
图形界面的客户端操作
SqlYOG
-
注册
-
新建连接
MySQL数据库的操作
数据库的操作
- 创建数据库
CREATE DATABASE imust
- 删除数据
DROP DATABASE imust_bak;
表的操作
表的创建
CREATE TABLE users(
-- 列的定义
id INT PRIMARY KEY AUTO_INCREMENT ,
username VARCHAR(50),
PASSWORD VARCHAR(50),
last_login DATETIME,
up_time DATETIME,
c_time DATETIME
)
表的赋值
– 备份表
– 1 仅仅备份数据结构
– 给users表备份表结构到新表user_bak
CREATE TABLE user_bak LIKE users ;
CREATE TABLE trade_order_bak LIKE trade_order ;
– 2 备份数据结构 +数据
CREATE TABLE trade_order_data SELECT * FROM trade_order
数据的基本操作
DML：数据插入、删除数据、更新数据
DQL：查询数据
数据的插入
-- 插入数据
INSERT INTO users
(username,PASSWORD,last_login,up_time,c_time)
VALUES
('admin','123456','2022-02-21 14:58:01','2022-02-21 14:58:01','2022-02-21 14:58:01')
-- 忽略字段枚举
INSERT INTO users
(id,username,PASSWORD,last_login,up_time,c_time)
VALUES
(2,'root','abcdef','2022-02-21 14:58:01','2022-02-21 14:58:01','2022-02-21 14:58:01')
INSERT INTO users
VALUES
(3,'jshand','qwert','2022-02-21 14:58:01','2022-02-21 14:58:01','2022-02-21 14:58:01')
-- 一次插入多条数据
INSERT INTO users
(username,PASSWORD,last_login,up_time,c_time)
VALUES
('acc01','qwert','2022-02-21 14:58:01','2022-02-21 14:58:01','2022-02-21 14:58:01'),
('acc02','qwert','2022-02-21 14:58:01','2022-02-21 14:58:01','2022-02-21 14:58:01'),
('acc03','qwert','2022-02-21 14:58:01','2022-02-21 14:58:01','2022-02-21 14:58:01'),
('acc04','qwert','2022-02-21 14:58:01','2022-02-21 14:58:01','2022-02-21 14:58:01');
删除数据
-- 删除的操作 [慎重操作]
-- 删除数据的时候一般情况下添加过滤条件
DELETE FROM users WHERE id = 5
修改数据
-- 修改数据
UPDATE
users
SET
PASSWORD = '987654321',
up_time = '2022-02-21 15:09:50'
WHERE id = 6
数据查询
语法： select (column1,[column2,cloumn3]) from table
-- 查询sql
SELECT id ,username,PASSWORD,last_login,up_time,c_time FROM users
-- 开发的时候可以使用，生成代码不能用
SELECT * FROM users
运算符
查询的运算符， 去重。 distinct
去除重复
-- 去除重复
SELECT DISTINCT NAME FROM address;
算数运算(±*/)
-- 查询所有订单id 和金额
SELECT order_id,amount FROM trade_order;
-- 查询订单8折的总金额
SELECT order_id,amount, amount*0.8 FROM trade_order;
SELECT order_id,amount, amount-10 FROM trade_order;
-- 列的别名
SELECT order_id,amount, amount/10 AS '除以10' FROM trade_order;
SELECT order_id,amount, amount/10 AS amount10 FROM trade_order;
SELECT order_id,amount, amount/10 amount10 FROM trade_order;
比较运算
=,!= ,<> ,>,<
-- 比较运算符
-- 查询订单总金额大于100的给与打折
SELECT order_id,amount, amount*0.8 FROM trade_order WHERE amount >100;
SELECT order_id,amount, amount*0.8 FROM trade_order WHERE amount <100;
SELECT order_id,amount, amount*0.8 FROM trade_order WHERE amount <=30;
SELECT order_id,amount, amount*0.8 FROM trade_order WHERE amount >=800;
SELECT order_id,amount, amount*0.8 FROM trade_order WHERE amount <>30;
SELECT order_id,amount, amount*0.8 FROM trade_order WHERE amount != 30;
特殊的比较运算符
- 过滤区间 between and
-- 查询订单且 订单总金额在10--100
SELECT * FROM trade_order WHERE amount BETWEEN 10 AND 100;
-- 错误的写法 10应该放到前面
SELECT * FROM trade_order WHERE amount BETWEEN 100 AND 10;
SELECT * FROM trade_order WHERE o_time BETWEEN '2022-02-01 00:00:00' AND '2022-02-28 23:59:59';
SELECT * FROM address WHERE province BETWEEN '辽宁省' AND '辽宁省1'
-- 尽量少用这个
SELECT * FROM address WHERE id = '2'
SELECT * FROM address WHERE id = 2
在写条件查询的时候尽量按照相同的数据类型编写SQL语句
- 跟某一个值相似(不相似)
-- 查询所有 姓张的收货地址
SELECT * FROM address;
-- % 模糊匹配0到多个字符
SELECT * FROM address WHERE NAME LIKE '张%'
-- _有且仅有一个
SELECT * FROM address WHERE telphone LIKE '18404_75932'
CREATE TABLE `dept` (
`deptno` INT(2) NOT NULL,
`dname` VARCHAR(14) DEFAULT NULL,
`loc` VARCHAR(13) DEFAULT NULL,
PRIMARY KEY (`deptno`)
) ENGINE=INNODB DEFAULT CHARSET=utf8;
INSERT INTO `dept`(`deptno`,`dname`,`loc`) VALUES (10,'ACCOUNTING','NEW YORK'),(20,'RESEARCH','DALLAS'),(30,'SALES','CHICAGO'),(40,'OPERATIONS','BOSTON');
CREATE TABLE `emp` (
`empno` INT(4) NOT NULL,
`ename` VARCHAR(10) DEFAULT NULL,
`job` VARCHAR(9) DEFAULT NULL,
`mgr` INT(4) DEFAULT NULL,
`hiredate` DATE DEFAULT NULL,
`sal` DECIMAL(7,2) DEFAULT NULL,
`comm` DECIMAL(7,2) DEFAULT NULL,
`deptno` INT(2) DEFAULT NULL,
PRIMARY KEY (`empno`)
) ENGINE=INNODB DEFAULT CHARSET=utf8;
INSERT INTO `emp`(`empno`,`ename`,`job`,`mgr`,`hiredate`,`sal`,`comm`,`deptno`) VALUES (1,'dog','code',7369,'2018-06-05','5000.00','5000.00',10),(7369,'SMITH','CLERK',7902,'1980-12-17','800.00',NULL,20),(7499,'ALLEN','SALESMAN',7698,'1981-02-20','1600.00','300.00',30),(7521,'WARD','SALESMAN',7698,'1981-02-22','1250.00','500.00',30),(7566,'JONES','MANAGER',7839,'1981-04-02','2975.00',NULL,20),(7654,'MARTIN','SALESMAN',7698,'1981-09-28','1250.00','1400.00',30),(7698,'BLAKE','MANAGER',7839,'1981-05-01','2850.00',NULL,30),(7788,'SCOTT','ANALYST',7566,'1987-04-19','3000.00',NULL,20),(7839,'KING','PRESIDENT',NULL,'1981-11-17','5000.00',NULL,10),(7844,'TURNER','SALESMAN',7698,'1981-09-08','1500.00','0.00',30),(7876,'ADAMS','CLERK',7788,'1987-05-23','1100.00',NULL,20),(7900,'JAMES','CLERK',7698,'1981-12-03','950.00',NULL,30),(7902,'FORD','ANALYST',7566,'1981-12-03','3000.00',NULL,20),(7934,'MILLER','CLERK',7782,'1982-01-23','1300.00',NULL,10);
-- 查询名字里面有A所有员工
SELECT * FROM emp WHERE ename LIKE '%A%' ;
-- 查询名字里面没有A所有员工
SELECT * FROM emp WHERE ename NOT LIKE '%A%' ;
- 某一个值空的(非空)
-- 查询没有奖金的人员 NULL 代表空值，
-- null不和任何值相等,包括自身
-- null != 1
-- null != '1'
-- null != null
SELECT * FROM emp WHERE comm IS NULL
SELECT * FROM emp WHERE comm IS NOT NULL
-- =0 是否包含 null
SELECT * FROM emp WHERE comm = 0
-- 查询奖金不为0 NULL不参与比较运算算
SELECT * FROM emp WHERE comm <> 0
- 在某些数值范围内的
-- 查询员工，部门编号是10和30
-- in 不走索引，无法提高查询效率
-- in最大个数是1000
SELECT * FROM emp WHERE deptno IN (10,30);
SELECT * FROM emp WHERE deptno NOT IN (10,30);
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