到底是什么原因才导致 select * 效率低下的?

https://mp.weixin.qq.com/s/GNNVZqI5GAMRwZFK41QWRA

 

回表，索引覆盖定义

https://www.cnblogs.com/wang-meng/p/ae6d1c4a7b553e9a5c8f46b67fb3e3aa.html

https://www.cnblogs.com/myseries/p/11265849.html