mysql入门教程

一、下载安装
1、安装前环境准备
(1)检查是否已经安装过mysql，执行命令
rpm -qa | grep mysql
-qa q代表query，a代表all

如果已存在，则执行卸载命令 后边为Mysql目录;
rpm -e --nodeps mysql-xxxx

(2)查询所有Mysql对应的文件夹;whereis 将和xxx文件相关的文件都查找出来
find / -name mysql

删除相关目录或文件
rm -rf xxx/mysql

验证是否删除完毕
find / -name mysql

(3)检查mysql用户组和用户是否存在，如果没有，则创建
cat /etc/group | grep mysql
cat /etc/passwd |grep mysql
groupadd mysql
useradd -r -g mysql mysql

2、下载安装mysql
先去官网选择Yum 资源包，地址为：https://dev.mysql.com/downloads/repo/yum/，根据linux版本下载rpm包，如centos6下载mysql80-community-release-el6-4.noarch.rpm
wget http://repo.mysql.com/mysql80-community-release-el6-4.noarch.rpm
rpm -ivh mysql80-community-release-el6-4.noarch.rpm
yum clean all
yum makecache
yum install mysql-community-server

验证mysql是否成功安装：mysqladmin --version

其中一些命令解释：
wget 文件下载命令;
rpm -ivh 安装 -Uvh 升级 -e 卸载 -q 查询是否安装安装(不带.rpm) -qi 查询安装情况;
yum clean all 清除缓存;yum makecache 是将软件包信息缓存,以提高速度；
yum repolist all | grep mysql 显示所有仓库,这里可以通过enable/disable 切换mysql版本 ，如使用mysql80而不使用mysql57
yum-config-manager --disable mysql80-community ;yum-config-manager --enable mysql57-community

验证mysql是否安装：mysqladmin --version

查看安装路径 whereis mysql

二、启动mysql
/etc/init.d/mysqld start
启动时候mysql会输出初始密码，查看log文件（cat /var/log/mysqld.log），能看到
A temporary password is generated for root@localhost: 9/ivBD=toQI9
9/ivBD=toQI9就是你的初始密码

后续启动：service mysqld start

**登录： mysql -u root -p
再粘贴上上面的密码
修改密码：
mysql>ALTER USER ‘root’@‘localhost’ IDENTIFIED BY ‘Ppp11111111!’;
查看是否能正常使用：
mysql>showdatabases;
mysql>use mysql;
mysql>exit 退出

三、整合springBoot/mybatis
1.创建表结构，并插入测试数据

CREATE TABLE `t00_user` (
  `user_id` varchar(64) DEFAULT NULL,
  `user_name` varchar(512) DEFAULT NULL
) ;
insert into t00_user values ('3322','马宝国');
insert into t00_user values ('5566','蔡徐坤');
insert into t00_user values ('8899','面筋哥');

2.修改配置文件
(1).在pom.xml文件中添加

		
        <dependency>
            <groupId>mysqlgroupId>
            <artifactId>mysql-connector-javaartifactId>
            <scope>runtimescope>
        dependency>

        
        <dependency>
            <groupId>org.mybatis.spring.bootgroupId>
            <artifactId>mybatis-spring-boot-starterartifactId>
            <version>2.1.0version>
        dependency>

(2)在application.yml文件中添加

server:
  port: 8080
spring:
  datasource:
    driver-class-name: com.mysql.jdbc.Driver
    #不加allowPublicKeyRetrieval=true会报SQLNonTransientConnectionException
    url: jdbc:mysql://192.168.124.128:3306/mysql?characterEncoding=utf-8&useSSL=false&allowPublicKeyRetrieval=true
    username: root
    password: Ppp11111111!

mybatis:
  #扫描mapper文件，Mapper文件一般放到resource下，如果放在java目录下，需要在pom文件的bulid标签下将.xml放到include下
  mapper-locations: classpath:mapping/*Mapper.xml

3.项目代码编写
(1)按照图示创建文件夹及文件，项目结构目录如下：

(2)代码编写
①UserController.java

package com.example.springb_web.controller;

import com.example.springb_web.dao.User;
import com.example.springb_web.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

import java.util.List;

@Controller
public class UserController {

    @Autowired
    private UserService userService;

    @RequestMapping(value="/getUser")
    @ResponseBody
    public List<User> test(){
        List<User> user = userService.getUser();
        return user;
    }

}

②User.java

package com.example.springb_web.dao;

public class User {
    private String user_id;
    private String user_name;

    public String getUser_id() {
        return user_id;
    }

    public void setUser_id(String user_id) {
        this.user_id = user_id;
    }

    public String getUser_name() {
        return user_name;
    }

    public void setUser_name(String user_name) {
        this.user_name = user_name;
    }
}

③UserDAO.java

package com.example.springb_web.mapper;

import com.example.springb_web.dao.User;
import java.util.List;

public interface UserDAO {

    List<User> getUser();
}

④UserService.java、UserServiceImpl.java

package com.example.springb_web.service;

import com.example.springb_web.dao.User;
import org.springframework.stereotype.Service;

import java.util.List;

public interface UserService {

    public List<User> getUser();
}

package com.example.springb_web.service.impl;

import com.example.springb_web.dao.User;
import com.example.springb_web.mapper.UserDAO;
import com.example.springb_web.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;

@Service("userService")
public class UserServiceImpl implements UserService {

    @Autowired
    private UserDAO userDAO;

    @Override
    public List<User> getUser() {
        return userDAO.getUser();
    }
}

⑤UserMapper.xml，注意namespace和resultType路径不能错

DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
<mapper namespace="com.example.springb_web.mapper.UserDAO">
    <select id="getUser" resultType="com.example.springb_web.dao.User">
        SELECT * FROM t00_user
    select>
mapper>

⑥SpringbWebApplication.java，这里主要是加上注解MapperScan

package com.example.springb_web;

import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
@MapperScan("com.example.springb_web.mapper")//使用MapperScan批量扫描所有的Mapper接口；
public class SpringbWebApplication {

    public static void main(String[] args) {
        SpringApplication.run(SpringbWebApplication.class, args);
    }

}

(3)结果验证：右击SpringbWebApplication文件，点击Debug 'SpringbWebApplication’启动。
输入网址http://localhost:8080/getUser
看到结果如下：

(4)权限问题：host is not allowed to connect…
mysql>update user set host = ‘%’ where user = ‘root’;
mysql>flush privileges;