WebOct 21, 2024 · Mysql Explain工具介绍 1.Explain的使用 Explain select * from tb_test; 查询结果如下图： 2.Explain分析 select_type： 这个字段意思是查询类型，它有很多个值，这里就只介绍几种常见的值: (1)simple: 简单查询不包含子查询或union； (2)primary: 复杂查询最层的select； (3)subquery: 在from之前的子查询； (4)derived: 在from之后的子 ... Web做一个积极的人 编码、改bug、提升自己 我有一个乐园，面向编程，春暖花开！ 昨天分享了Mysql中的 explain 命令，使用 explain 来分析 select 语句的运行效果，如 ：explain可以获得select语句使用的索引情况、排序的情况等等。链接：顺便提到了explain extended，有小伙伴留言说想知道一些explain extended，那 ...
MySQL EXPLAIN语句中的extended 选项介绍 - PHP中文网
WebThe MySQL 5.7 documentation states:. The filtered column indicates an estimated percentage of table rows that will be filtered by the table condition. That is, rows shows the estimated number of rows examined and rows × filtered / 100 shows the number of rows that will be joined with previous tables. To attempt to understand this better, I tried it out … WebWith the help of EXPLAIN, you can see where you should add indexes to tables so that the statement executes faster by using indexes to find rows.You can also use EXPLAIN to check whether the optimizer joins the tables in an optimal order. To give a hint to the optimizer to use a join order corresponding to the order in which the tables are named in a SELECT … eyes makeup pics
Using EXPLAIN to Write Better MySQL Queries — SitePoint
WebJan 13, 2024 · explain EXTENDED SELECT count() from OORDER where O_CARRIER_ID<10000; 网上的教程都是explain EXTENDED，后来查看官方文档发现. … Webmysql> explain select * from film_actor where film_id > 1; 4） Using temporary ：mysql需要创建一张临时表来处理查询。. 出现这种情况一般是要进行优化的，首先是想到用索引来优化。. 1. actor.name没有索引，此时创建了张临时表来distinct. mysql> explain select distinct name from actor; 2. film ... WebThe EXPLAIN statement provides information about how MySQL executes statements: EXPLAIN works with SELECT , DELETE , INSERT , REPLACE, and UPDATE statements. In MySQL 8.0.19 and later, it also works with TABLE statements. When EXPLAIN is used with an explainable statement, MySQL displays information from the optimizer about the … eyes made of pure plastic