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 idx1 ON tab_index;
Query OK, 55 rows affected (0.01 sec)
Records: 55 Duplicates: 0 Warnings: 0
mysql> ALTER TABLE tab_index
-> ADD INDEX idx2(age,dte);
Query OK, 55 rows affected (0.01 sec)
Records: 55 Duplicates: 0 Warnings: 0
按照上一篇的测试结论应该是：
(age) 走索引，且索引长度最短
(age,id)走索引，且索引长度最短
(age,dte)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
重新测试看下：
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 | ref | idx2 | idx2 | 5 | const | 1 | Using where |
+----+-------------+-----------+------+---------------+------+---------+-------+------+-------------+
1 row in set (0.01 sec)
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 | idx2 | idx2 | 5 | 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' ;
+----+-------------+-----------+-------+---------------+------+---------+------+------+-------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+-----------+-------+---------------+------+---------+------+------+-------------+
| 1 | SIMPLE | tab_index | range | idx2 | idx2 | 14 | NULL | 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 | range | idx2 | idx2 | 14 | NULL | 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 | range | idx2 | idx2 | 14 | NULL | 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 | range | idx2 | idx2 | 14 | NULL | 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 | range | idx2 | idx2 | 14 | NULL | 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 | range | idx2 | idx2 | 14 | NULL | 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 | range | idx2 | idx2 | 14 | NULL | 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 | range | idx2 | idx2 | 14 | NULL | 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 | range | idx2 | idx2 | 14 | NULL | 1 | Using where |
+----+-------------+-----------+-------+---------------+------+---------+------+------+-------------+
1 row in set (0.00 sec)
结论正确！
MySQL 联合索引测试2的更多相关文章
- 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_ ...
- 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
- Git_操作标签
如果标签打错了,也可以删除: $ git tag -d v0.1 Deleted tag 'v0.1' (was e078af9) 因为创建的标签都只存储在本地,不会自动推送到远程.所以,打错的标签可 ...
- 封装scroll.js 获取滚动条的值
function Obj(){} Obj.prototype={ scroll:function(){ /* 主要是做兼容处理 这里必须时!=null 因为默认值和每次滚动的时侯 都可以值为0 但是 ...
- Cocos2d-x移植android增加震动效果
cpp部分通过jni调用java静态函数 头文件: #include <jni.h> #include "cocos2d.h" #include "platf ...
- jquery实现回车键触发事件
键盘事件有3: keydown,keypress,keyup,分别是按下,按着没上抬,上抬键盘 . 正确代码为: $(document).keyup(function(event){ if(event ...
- yield的使用
参考: http://www.ibm.com/developerworks/cn/opensource/os-cn-python-yield/ http://blog.csdn.net/alvine0 ...
- Android中高亮变色显示文本中的关键字
应该是好久没有写有关技术类的文章了,前天还有人在群里问我,说群主很长时间没有分享干货了,今天分享一篇Android中TextView在大段的文字内容中如何让关键字高亮变色的文章 ,希望对大家有所帮助, ...
- 在mac上命令行里面如何打开文本编辑器？
在mac上命令行里面如何打开文本编辑器? 在linux命令行terminal上使用gedit直接就可以打开文本文件 那么在mac上面如何操作呢? 使用:open -a TextEdit setti ...
- WebService—CXF整合Spring实现接口发布和调用过程
一.CXF整合Spring实现接口发布 发布过程如下: 1.引入jar包(基于maven管理) <!-- cxf --> <dependency> <groupId> ...
- hadoop基准測试
写測试hadoop jarhadoop-0.20.2-test.jar TestDFSIO -write -nrFiles 10 -fileSize 1000 ----- TestDFSIO ---- ...
- java中需要用equals来判断两个字符串值是否相等
在C++中,两个字符串比较的代码可以为: (string1==string2) 但在java中,这个代码即使在两个字符串完全相同的情况下也会返回false Java中必须使用string1.equal ...