EXPLAIN 查询语句
![](https://img.haomeiwen.com/i12309425/ebf018e1cab077f3.png)
重构查询的方式
1.多个简单查询还是单个复杂查询
2.切分查询
![](https://img.haomeiwen.com/i12309425/5d78e545a79a5b8d.png)
3.分解关联查询
![](https://img.haomeiwen.com/i12309425/b3bff79757786cb0.png)
查询执行的基础
![](https://img.haomeiwen.com/i12309425/95b0dcd21b113271.png)
查询状态
![](https://img.haomeiwen.com/i12309425/d50bf9b10476a982.png)
查询优化器的局限性
1.关联子查询
![](https://img.haomeiwen.com/i12309425/f8217649648bdfd0.png)
2.union 的限制
![](https://img.haomeiwen.com/i12309425/4a52ebd17ec1bec1.png)
3.同一表上查询和更新
![](https://img.haomeiwen.com/i12309425/10191b573aeff64e.png)
查询优化器的提示
![](https://img.haomeiwen.com/i12309425/a7732785abb263fb.png)
![](https://img.haomeiwen.com/i12309425/8d386152fa3109b5.png)
![](https://img.haomeiwen.com/i12309425/775684175bec1c2c.png)
![](https://img.haomeiwen.com/i12309425/5f362a377b7fa425.png)
特定查询的优化
1.优化count()查询
最好使用count(*)
简单的优化
![](https://img.haomeiwen.com/i12309425/215906273b62708d.png)
![](https://img.haomeiwen.com/i12309425/0b638392bbf2a36e.png)
2.优化关联查询
![](https://img.haomeiwen.com/i12309425/6c5ab58d1435b5a2.png)
3.优化limit分页
![](https://img.haomeiwen.com/i12309425/610454377fc718ee.png)
![](https://img.haomeiwen.com/i12309425/326e42ff9f3d2d75.png)
EXPLAIN 查询语句
1.多个简单查询还是单个复杂查询
2.切分查询
3.分解关联查询
查询状态
查询优化器的局限性
1.关联子查询
2.union 的限制
3.同一表上查询和更新
1.优化count()查询
最好使用count(*)
简单的优化
2.优化关联查询
3.优化limit分页
本文标题:《高性能mysql》笔记-查询优化
本文链接:https://www.haomeiwen.com/subject/zkepiftx.html
网友评论