1linux环境mysql安装运行1.1下载案例在/usr/local/src，下载msqlwgethttp://dev.mysql.com/get/Downloads/MySQL-5.7/mysql-5.7.14-1.el7.x86_64.rpm-bundle.tar1.2安装在/usr/local/src创建mysql-install.sh，并运行#!/bin/bashmkdir/usr/lo......

问题：前段时间，一朋友面试的时候，问到sql优化时，说sql查询效率exists大于in，果真如此？准备新建users/*用户表*/droptableifexistsusers;createtableusers(idintprimarykeyauto_increment,namevarchar(20));insertintousers(name)values('A');insertintouser......