bitsCN.com
关于mysql的MERGE存储引擎简单例子
作用:可以将多个表结构相同的表 和合并到一个表中
版本支持:mysql5.1
如下例子:
假设有如下几个表:结构完全相同 article_0,article_1,article_2,article_3,
-- Table "article_0" DDLCREATE TABLE `article_0` ( `id` bigint(20) NOT NULL, `subject` varchar(200) NOT NULL, `content` text NOT NULL, PRIMARY KEY (`id`)) ENGINE=MyISAM DEFAULT CHARSET=utf8;-- Table "article_1" DDLCREATE TABLE `article_1` ( `id` bigint(20) NOT NULL, `subject` varchar(200) NOT NULL, `content` text NOT NULL, PRIMARY KEY (`id`)) ENGINE=MyISAM DEFAULT CHARSET=utf8;-- Table "article_2" DDLCREATE TABLE `article_2` ( `id` bigint(20) NOT NULL, `subject` varchar(200) NOT NULL, `content` text NOT NULL, PRIMARY KEY (`id`)) ENGINE=MyISAM DEFAULT CHARSET=utf8;-- Table "article_3" DDLCREATE TABLE `article_3` ( `id` bigint(20) NOT NULL, `subject` varchar(200) NOT NULL, `content` text NOT NULL, PRIMARY KEY (`id`)) ENGINE=MyISAM DEFAULT CHARSET=utf8;
建立总表:article_total 结构如下:
-- Table "article_total" DDLCREATE TABLE `article_total` ( `id` bigint(20) NOT NULL, `subject` varchar(200) NOT NULL, `content` text NOT NULL, PRIMARY KEY (`id`)) ENGINE=MRG_MyISAM DEFAULT CHARSET=utf8 UNION=(`article_0`,`article_1`,`article_2`,`article_3`);
那么 article_total 表的内容就包含了article_0`,`article_1`,`article_2`,`article_3`的内容
select * from article_total 表的结果就是各个表述数据合并的内容
修改合并哪些子表的命令:
ALTER TABLE article_total union =(article_0,article_1,article_2,article_3)
bitsCN.com

本篇文章给大家带来了关于mysql的相关知识,其中主要介绍了关于架构原理的相关内容,MySQL Server架构自顶向下大致可以分网络连接层、服务层、存储引擎层和系统文件层,下面一起来看一下,希望对大家有帮助。

在mysql中,可以利用char()和REPLACE()函数来替换换行符;REPLACE()函数可以用新字符串替换列中的换行符,而换行符可使用“char(13)”来表示,语法为“replace(字段名,char(13),'新字符串') ”。

方法:1、利用right函数,语法为“update 表名 set 指定字段 = right(指定字段, length(指定字段)-1)...”;2、利用substring函数,语法为“select substring(指定字段,2)..”。

mysql的msi与zip版本的区别:1、zip包含的安装程序是一种主动安装,而msi包含的是被installer所用的安装文件以提交请求的方式安装;2、zip是一种数据压缩和文档存储的文件格式,msi是微软格式的安装包。

转换方法:1、利用cast函数,语法“select * from 表名 order by cast(字段名 as SIGNED)”;2、利用“select * from 表名 order by CONVERT(字段名,SIGNED)”语句。

本篇文章给大家带来了关于mysql的相关知识,其中主要介绍了关于MySQL复制技术的相关问题,包括了异步复制、半同步复制等等内容,下面一起来看一下,希望对大家有帮助。

本篇文章给大家带来了关于mysql的相关知识,其中主要介绍了mysql高级篇的一些问题,包括了索引是什么、索引底层实现等等问题,下面一起来看一下,希望对大家有帮助。

在mysql中,可以利用REGEXP运算符判断数据是否是数字类型,语法为“String REGEXP '[^0-9.]'”;该运算符是正则表达式的缩写,若数据字符中含有数字时,返回的结果是true,反之返回的结果是false。


Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

AI Hentai Generator
Generate AI Hentai for free.

Hot Article

Hot Tools

DVWA
Damn Vulnerable Web App (DVWA) is a PHP/MySQL web application that is very vulnerable. Its main goals are to be an aid for security professionals to test their skills and tools in a legal environment, to help web developers better understand the process of securing web applications, and to help teachers/students teach/learn in a classroom environment Web application security. The goal of DVWA is to practice some of the most common web vulnerabilities through a simple and straightforward interface, with varying degrees of difficulty. Please note that this software

SublimeText3 Mac version
God-level code editing software (SublimeText3)

PhpStorm Mac version
The latest (2018.2.1) professional PHP integrated development tool

Safe Exam Browser
Safe Exam Browser is a secure browser environment for taking online exams securely. This software turns any computer into a secure workstation. It controls access to any utility and prevents students from using unauthorized resources.

Zend Studio 13.0.1
Powerful PHP integrated development environment
