SQL语句执行过程

编码原则：对于已有的代码，我们要做到 对扩展开放，对修改关闭。 select <1> from <2> where <3> group by <4> having <5> order by <6> limit <7> WHERE过滤→分组→聚合函数 ******SQL的执行顺序如下****** –第一步：执行 from –第二步：分组前的条件过滤 where –第三步：分组 group by –第四步：执行投影列 select –第五步：分组后的条件过滤 having –第六步：执行排序 order by –第七步：执行选择几行输出 limit

MySQL学习路线

0、MySQL菜鸟教程

https://www.runoob.com/mysql/mysql-install.html

1、Mac上安装MySQL

https://www.jianshu.com/p/0c701a4e7976

/usr/local/mysql/bin (1)Use Strong Passord Encryption: MySQL root user pd=admin000111 (2)Use Legacy Passord Encryption: MySQL root user pd=admin0001112 export JAVA_HOME=/Library/Java/JavaVirtualMachines/jdk1.8.0_111.jdk/Contents/Home export PATH=$PATH:$JAVA_HOME/bin export M2_HOME=/Library/maven/apache-maven-3.5.3 export PATH=$PATH:$M2_HOME/bin export MYSQL_HOME=/usr/local/mysql export PATH=$PATH:$MYSQL_HOME/bin //登陆步骤： source ~/.bash_profile mysql -u root -p 密：admin0001112

2、解决MAC下每次都要执行soource ~/.bash_profile配置环境变量才能生效的问题

MySQL客户端SequelPro连接数据库失败：https://www.jianshu.com/p/6b4fa7b87547

（1）官网：https://dev.mysql.com/downloads/mysql/、https://blog.csdn.net/RunIntoLove/article/details/51422787

（2）参考：https://jingyan.baidu.com/article/fa4125ac0e3c2928ac709204.html