mysql中key 、primary key 、unique key 与index区别
https://blog.csdn.net/nanamasuda/article/details/52543177
mysql 中UNIQUE KEY 到底是约束还是索引？
https://blog.csdn.net/freehappyness/article/details/78501159
mysql查询性能分析(show status,show profile,explain)
https://blog.csdn.net/wwwbbb8510/article/details/7593729
分析Query 语句对系统性能的影响
https://blog.csdn.net/ljasdf123/article/details/11722079
Mysql Query Profiler
https://www.xuebuyuan.com/1760958.html
mysql中explain的type的解释
https://blog.csdn.net/dennis211/article/details/78170079
MySQL EXPLAIN type类型说明
https://blog.csdn.net/qq_27676247/article/details/79387637
https://blog.csdn.net/codingtu/article/details/79538166
