MySQL 联合索引测试
搭建测试环境
1：创建表
CREATE TABLE tab_index
(id int(5),
age int(3),
dte datetime);
2：插入测试数据
INSERT INTO tab_index
VALUES(1,'2012-05-13',23);
INSERT INTO tab_index
VALUES(2,'2012-05-13',23);
INSERT INTO tab_index
VALUES(3,'2012-05-13',31);
INSERT INTO tab_index
VALUES(4,'2012-05-13',32);
INSERT INTO tab_index
VALUES(5,'2012-05-13',33);
INSERT INTO tab_index
VALUES(6,'2012-06-13',34);
INSERT INTO tab_index
VALUES(7,'2012-07-13',35);
INSERT INTO tab_index
VALUES(8,'2012-08-13',36);
INSERT INTO tab_index
VALUES(9,'2012-09-13',37);
INSERT INTO tab_index
VALUES(10,'2012-05-17',38);
INSERT INTO tab_index
VALUES(11,'2012-05-19',39);
INSERT INTO tab_index
VALUES(1,'2012-05-13',23);
INSERT INTO tab_index
VALUES(2,'2012-05-13',23);
INSERT INTO tab_index
VALUES(3,'2012-05-13',31);
INSERT INTO tab_index
VALUES(4,'2012-05-13',32);
INSERT INTO tab_index
VALUES(5,'2012-05-13',33);
INSERT INTO tab_index
VALUES(6,'2012-06-13',34);
INSERT INTO tab_index
VALUES(7,'2012-07-13',35);
INSERT INTO tab_index
VALUES(8,'2012-08-13',36);
INSERT INTO tab_index
VALUES(9,'2012-09-13',37);
INSERT INTO tab_index
VALUES(10,'2012-05-17',38);
INSERT INTO tab_index
VALUES(11,'2012-05-19',39);
INSERT INTO tab_index
VALUES(1,'2012-05-13',23);
INSERT INTO tab_index
VALUES(2,'2015-05-13',23);
INSERT INTO tab_index
VALUES(3,'2012-05-13',31);
INSERT INTO tab_index
VALUES(4,'2012-05-13',32);
INSERT INTO tab_index
VALUES(5,'2012-05-13',33);
INSERT INTO tab_index
VALUES(6,'2012-06-13',34);
INSERT INTO tab_index
VALUES(7,'2013-07-13',35);
INSERT INTO tab_index
VALUES(8,'2012-08-13',36);
INSERT INTO tab_index
VALUES(9,'2012-09-13',37);
INSERT INTO tab_index
VALUES(10,'2012-05-17',38);
INSERT INTO tab_index
VALUES(11,'2011-05-19',39);
INSERT INTO tab_index
VALUES(1,'2012-05-13',23);
INSERT INTO tab_index
VALUES(2,'2012-05-13',23);
INSERT INTO tab_index
VALUES(3,'2010-05-13',31);
INSERT INTO tab_index
VALUES(4,'2012-05-13',32);
INSERT INTO tab_index
VALUES(5,'2010-05-13',33);
INSERT INTO tab_index
VALUES(6,'2010-06-13',34);
INSERT INTO tab_index
VALUES(7,'2012-07-13',35);
INSERT INTO tab_index
VALUES(8,'2012-08-13',36);
INSERT INTO tab_index
VALUES(9,'2011-09-13',37);
INSERT INTO tab_index
VALUES(10,'2012-05-17',38);
INSERT INTO tab_index
VALUES(11,'2012-05-19',39);
INSERT INTO tab_index
VALUES(1,'2012-05-13',23);
INSERT INTO tab_index
VALUES(2,'2012-05-13',23);
INSERT INTO tab_index
VALUES(3,'2012-05-13',31);
INSERT INTO tab_index
VALUES(4,'2012-05-13',32);
INSERT INTO tab_index
VALUES(5,'2012-05-13',33);
INSERT INTO tab_index
VALUES(6,'2012-06-13',34);
INSERT INTO tab_index
VALUES(7,'2014-07-13',35);
INSERT INTO tab_index
VALUES(8,'2012-08-13',36);
INSERT INTO tab_index
VALUES(9,'2011-09-13',37);
INSERT INTO tab_index
VALUES(10,'2012-05-17',38);
INSERT INTO tab_index
VALUES(11,'2012-05-19',39);
3：创建id和age上的联合索引
CREATE INDEX idx1
ON tab_index(id,age);
4：开始测试
mysql> EXPLAIN SELECT id,dte,age
-> FROM tab_index
-> WHERE id=3;
+----+-------------+-----------+------+---------------+------+---------+-------+------+-------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+-----------+------+---------------+------+---------+-------+------+-------------+
| 1 | SIMPLE | tab_index | ref | idx1 | idx1 | 5 | const | 5 | Using where |
+----+-------------+-----------+------+---------------+------+---------+-------+------+-------------+
1 row in set (0.00 sec)
id=3走索引,age=31不走索引。很容易理解
mysql> EXPLAIN SELECT id,dte,age
-> FROM tab_index
-> WHERE age=31;
+----+-------------+-----------+------+---------------+------+---------+------+------+-------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+-----------+------+---------------+------+---------+------+------+-------------+
| 1 | SIMPLE | tab_index | ALL | NULL | NULL | NULL | NULL | 55 | Using where |
+----+-------------+-----------+------+---------------+------+---------+------+------+-------------+
1 row in set (0.00 sec)
mysql> EXPLAIN SELECT id,dte,age
-> FROM tab_index
-> WHERE id=3 AND age=31;
+----+-------------+-----------+------+---------------+------+---------+-------------+------+-------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+-----------+------+---------------+------+---------+-------------+------+-------------+
| 1 | SIMPLE | tab_index | ref | idx1 | idx1 | 10 | const,const | 1 | Using where |
+----+-------------+-----------+------+---------------+------+---------+-------------+------+-------------+
1 row in set (0.00 sec)
id=3 AND age=31 和 age=31 AND id=3都走索引了，但是索引长度跟之前不同
mysql> EXPLAIN SELECT id,dte,age
-> FROM tab_index
-> WHERE age=31 AND id=3 ;
+----+-------------+-----------+------+---------------+------+---------+-------------+------+-------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+-----------+------+---------------+------+---------+-------------+------+-------------+
| 1 | SIMPLE | tab_index | ref | idx1 | idx1 | 10 | const,const | 1 | Using where |
+----+-------------+-----------+------+---------------+------+---------+-------------+------+-------------+
1 row in set (0.00 sec)
mysql> EXPLAIN SELECT id,dte,age
-> FROM tab_index
-> WHERE id=3 AND age=31 AND dte BETWEEN '2011-05-13 00:00:00' AND '2013-05-13 00:00:00';
+----+-------------+-----------+------+---------------+------+---------+-------------+------+-------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+-----------+------+---------------+------+---------+-------------+------+-------------+
| 1 | SIMPLE | tab_index | ref | idx1 | idx1 | 10 | const,const | 1 | Using where |
+----+-------------+-----------+------+---------------+------+---------+-------------+------+-------------+
1 row in set (0.00 sec)
mysql> EXPLAIN SELECT id,dte,age
-> FROM tab_index
-> WHERE id=3 AND dte BETWEEN '2011-05-13 00:00:00' AND '2013-05-13 00:00:00' AND age=31;
+----+-------------+-----------+------+---------------+------+---------+-------------+------+-------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+-----------+------+---------------+------+---------+-------------+------+-------------+
| 1 | SIMPLE | tab_index | ref | idx1 | idx1 | 10 | const,const | 1 | Using where |
+----+-------------+-----------+------+---------------+------+---------+-------------+------+-------------+
1 row in set (0.00 sec)
mysql> EXPLAIN SELECT id,dte,age
-> FROM tab_index
-> WHERE dte BETWEEN '2011-05-13 00:00:00' AND '2013-05-13 00:00:00' AND id=3 AND age=31;
+----+-------------+-----------+------+---------------+------+---------+-------------+------+-------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+-----------+------+---------------+------+---------+-------------+------+-------------+
| 1 | SIMPLE | tab_index | ref | idx1 | idx1 | 10 | const,const | 1 | Using where |
+----+-------------+-----------+------+---------------+------+---------+-------------+------+-------------+
1 row in set (0.00 sec)
mysql> EXPLAIN SELECT id,dte,age
-> FROM tab_index
-> WHERE age=31 AND id=3 AND dte BETWEEN '2011-05-13 00:00:00' AND '2013-05-13 00:00:00';
+----+-------------+-----------+------+---------------+------+---------+-------------+------+-------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+-----------+------+---------------+------+---------+-------------+------+-------------+
| 1 | SIMPLE | tab_index | ref | idx1 | idx1 | 10 | const,const | 1 | Using where |
+----+-------------+-----------+------+---------------+------+---------+-------------+------+-------------+
1 row in set (0.00 sec)
mysql> EXPLAIN SELECT id,dte,age
-> FROM tab_index
-> WHERE age=31 AND dte BETWEEN '2011-05-13 00:00:00' AND '2013-05-13 00:00:00' AND id=3 ;
+----+-------------+-----------+------+---------------+------+---------+-------------+------+-------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+-----------+------+---------------+------+---------+-------------+------+-------------+
| 1 | SIMPLE | tab_index | ref | idx1 | idx1 | 10 | const,const | 1 | Using where |
+----+-------------+-----------+------+---------------+------+---------+-------------+------+-------------+
1 row in set (0.00 sec)
mysql> EXPLAIN SELECT id,dte,age
-> FROM tab_index
-> WHERE dte BETWEEN '2011-05-13 00:00:00' AND '2013-05-13 00:00:00' AND age=31 AND id=3 ;
+----+-------------+-----------+------+---------------+------+---------+-------------+------+-------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+-----------+------+---------------+------+---------+-------------+------+-------------+
| 1 | SIMPLE | tab_index | ref | idx1 | idx1 | 10 | const,const | 1 | Using where |
+----+-------------+-----------+------+---------------+------+---------+-------------+------+-------------+
1 row in set (0.00 sec)
另外其他几种情况，同学们自己尝试下以加深印象。
总结如下：
(id)走索引，且索引长度最短
(id,dte)走索引，且索引长度最短
(id,age)走索引，且索引长度最长
(id,age,dte)走索引，且索引长度最长
(id,dte,age)走索引，且索引长度最长
(dte,id,age)走索引，且索引长度最长
(dte,age,id)走索引，且索引长度最长
(age,dte,id)走索引，且索引长度最长
(age,id,dte)走索引，且索引长度最长
MySQL 联合索引测试的更多相关文章
- MySQL 联合索引测试2
接上一篇文章: http://www.cnblogs.com/xiaoit/p/4430300.html 1:首先删掉上一篇建立的索引,重新建立一个. mysql> DROP INDEX idx ...
- MySQL 联合索引测试3
接上一篇文章: http://www.cnblogs.com/xiaoit/p/4430387.html 有时候会出现某字段建立一个索引,但是查看执行计划的时候发现还是全扫了表? 可以强制走下索引看看 ...
- SQL Server中的联合主键、聚集索引、非聚集索引、mysql 联合索引
我们都知道在一个表中当需要2列以上才能确定记录的唯一性的时候,就需要用到联合主键,当建立联合主键以后,在查询数据的时候性能就会有很大的提升,不过并不是对联合主键的任何列单独查询的时候性能都会提升,但我 ...
- 三道MySQL联合索引面试题，淘汰80%的面试者，你能答对几道
众所周知MySQL联合索引遵循最左前缀匹配原则,在少数情况下也会不遵循(有兴趣,可以翻一下上篇文章). 创建联合索引的时候,建议优先把区分度高的字段放在第一列. 至于怎么统计区分度,可以按照下面这种方 ...
- MySQL 联合索引详解
MySQL 联合索引详解 联合索引又叫复合索引.对于复合索引:Mysql从左到右的使用索引中的字段,一个查询可以只使用索引中的一部份,但只能是最左侧部分.例如索引是key index (a,b,c ...
- mysql 联合索引(转)
http://blog.csdn.net/lmh12506/article/details/8879916 mysql 联合索引详解 联合索引又叫复合索引.对于复合索引:Mysql从左到右的使用索引中 ...
- MySQL联合索引VS单列索引
MySQL联合索引VS单列索引 以一个一千万数据量的表格为例 1. 建表建索引 USE foo; DROP TABLE IF EXISTS tmp; CREATE TABLE tmp ( id INT ...
- MySQL联合索引最左匹配范例
MySQL联合索引最左匹配范例 参考文章:http://blog.jobbole.com/24006/ 创建示例表. 示例表来自MySQL官方文档: https://dev.mysql.com/doc ...
- [转]mysql联合索引
mysql联合索引 命名规则:表名_字段名1.需要加索引的字段,要在where条件中2.数据量少的字段不需要加索引3.如果where条件中是OR关系,加索引不起作用4.符合最左原则 https:/ ...
随机推荐
- java中HashMap在多线程环境下引起CPU100%的问题解决
最近项目中出现了Tomcat占用CPU100%的情况,原以为是代码中出现死循环,后台使用jstack做了dump,发现是系统中不合理使用HashMap导致出现了死循环(注意不是死锁). 产生这个死循环 ...
- Android性能优化之渲染
Google近期在Udacity上发布了Android性能优化的在线课程,目前有三个篇章,分别从渲染,运算与内存,电量三个方面介绍了如何去优化性能,这些课程是Google之前在Youtube上发布的A ...
- 图之Dijkstra算法
Dijkstra算法是一种求单源最短路的算法,即从一个点开始到所有其他点的最短路.其步骤如下: c语言实现如下:(使用邻接矩阵存储) #include <stdio.h> #include ...
- [翻译] AsyncImageView 异步下载图片
AsyncImageView https://github.com/nicklockwood/AsyncImageView AsyncImageView is a simple extension ...
- Log4j输出格式控制
参数说明例子 %c 列出logger名字空间的全称,如果加上{<层数>}表示列出从最内层算起的指定层数的名字空间 log4j配置文件参数举例 输出显示媒介 假设当前logger名字空间是& ...
- ffmpeg 2.3版本号, 关于ffplay音视频同步的分析
近期学习播放器的一些东西.所以接触了ffmpeg,看源代码的过程中.就想了解一下ffplay是怎么处理音视频同步的,之前仅仅大概知道通过pts来进行同步,但对于怎样实现却不甚了解,所以想借助这个机会, ...
- 我所遭遇过的游戏中间件--FlashOcx
使用Flash做游戏界面的另一种方式是通过Abode提供flash.ocx处理Flash界面.将Flash图像通过GDI绘制出来后,再将图像数据拷贝到一个D3D的纹理结构中,最后由引擎的D3D接口进行 ...
- guess-number-higher-or-lower-ii
// https://discuss.leetcode.com/topic/51353/simple-dp-solution-with-explanation // https://en.wikipe ...
- 网络结构设计——负载均衡之LVS学习笔记（三）
LVS按个人理解的说就是将一台Linux服务器当作路由器等功能的技术.LVS---Linux虚拟服务器. LVS实现了三种IP负载均衡技术VS/NAT.VS/TUN.VS/DR. 今天简单分享一下我在 ...
- j2ee model1模型完成分页逻辑的实现 详解!
在显示用户全部信息的页面,在显示全部数据的时候,长长的滚动条,像是没有边界的天空一样, 让用户查看数据很不方便. 于是, 我们要把这些数据分页显示, 就像office的word一样,每页显示一定数量的 ...