ubuntu20.04安装MySQL5.6方法

ubuntu默认安装的是MySQL8.0版本，但是好多命令跟网上的老版本的不一样，对新手很不友好，所以这里安装MySQL5.6版本。
安装之前要把8.0版本的卸载干净。
1.添加镜像源

sudo vim /etc/apt/sources.list 
# 清华镜像源
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial main restricted universe multiverse
deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-updates main restricted universe multiverse
deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-updates main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-backports main restricted universe multiverse
deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-backports main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-security main restricted universe multiverse
deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-security main restricted universe multiverse

2.更新镜像源

sudo apt-get update
sudo apt-get upgrade  

3.安装MySQL

sudo apt-get install mysql-server-5.6
sudo apt-get install mysql-client-5.6