https://www.cnblogs.com/junrong624/p/7411679.html
https://www.cnblogs.com/shijianchuzhenzhi/p/6383117.html
3.mysql索引
https://wenku.baidu.com/view/f00c3cf9195f312b3169a545.html
4.mysql 数据库中一个表最多可存多少记录,在线等
https://bbs.csdn.net/wap/topics/310083469
5.为什么where条件中使用or索引不起作用？
https://blog.csdn.net/qq_32331073/article/details/79043490
6.mysql or条件可以使用索引而避免全表
https://blog.csdn.net/hguisu/article/details/7106159
7.MySql中UNION与UNION ALL的区别
https://blog.csdn.net/gang_strong/article/details/52161438
8.mysql索引和锁机制简介及SQL优化
https://wenku.baidu.com/view/3c0eec2025c52cc58bd6beb8.html?sxts=1534482900903
9.truncate与delete的区别
https://blog.csdn.net/my543843165/article/details/53696441
