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更新 MySql_index.md

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小柒2012
2018-09-13 16:51:41 +08:00
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数据库/MySql_index.md
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@@ -68,4 +68,8 @@ mysql查询只使用一个索引，因此如果where子句中已经使用了索
select * from users where YEAR(adddate)
```
#### 不使用NOT IN和操作
NOT IN和操作都不会使用索引将进行全表扫描。NOT IN可以NOT EXISTS代替，id3则可使用id>3 or id
NOT IN和操作都不会使用索引将进行全表扫描。NOT IN可以NOT EXISTS代替，id3则可使用id>3 or id
## 参考阅读
[MySQL索引背后的数据结构及算法原理](http://blog.codinglabs.org/articles/theory-of-mysql-index.html)