Table of Contents
用SHOW语句获取元数据
从INFORMATION_SCHEMA数据库里查询相关表
从命令行获取元数据
Home Database Mysql Tutorial [MySQL] 获取元数据的步骤

[MySQL] 获取元数据的步骤

Jun 07, 2016 pm 04:14 PM
mysql data method step Obtain

[MySQL] 获取元数据的方法 MySQL提供了以下三种方法用于获取数据库对象的元数据: 1)show语句 2)从INFORMATION_SCHEMA数据库里查询相关表 3)命令行程序,如mysqlshow, mysqldump 用SHOW语句获取元数据 MySQL用show语句获取元数据是最常用的方法,下面提供

[MySQL] 获取元数据的方法

MySQL提供了以下三种方法用于获取数据库对象的元数据:

1)show语句

2)从INFORMATION_SCHEMA数据库里查询相关表

3)命令行程序,如mysqlshow, mysqldump


用SHOW语句获取元数据

MySQL用show语句获取元数据是最常用的方法,下面提供了几种典型用法:

show databases;  --列出所有数据库
show create database db_name;  --查看数据库的DDL
show tables; --列出默认数据库的所有表
show tables from db_name;  --列出指定数据库的所有表
show table status;  --查看表的描述性信息
show table status from db_name;
show create table tbl_name;  --查看表的DDL
show columns from tbl_name;  --查看列信息
show index from tbl_name;  --查看索引信息
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有几种show语句还可以带有一条like 'pattern'字句,用来限制语句的输出范围,其中'pattern'允许包含'%'和'_'通配符,比如下面这条语句返回domaininfo表中以s开头的所有列:

show columns from domaininfo like 's%';
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像上面这张支持like字句的所有show都可以改写成一条where字句,如:

show columns from domaininfo where field='sysdomain';
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注:desc tbl_name和explain tbl_name的效果和show columns from tbl_name一致。


从INFORMATION_SCHEMA数据库里查询相关表

INFORMATION_SCHEMA是MySQL自带的一个系统数据库,它里面存储了所有的元数据,通过select里面的相关表就可以获取你想要的元数据。和show语句相比,它比较麻烦,但它的好处是标准的SQL语句,更具有可移植性,且更灵活,可以通过各种表达式获取你真正需要的信息。


从命令行获取元数据

前面两种方法都必须得在MySQL命令行里执行,而mysqlshow和mysqldump提供了从OS命令行获取元数据库的方法,如:
mysqlshow  --列出所有数据库
mysqlshow db_name  --列出给定数据库的所有表
mysqlshow db_name tbl_name  --列出给定数据库表的所有列
mysqlshow --keys db_name tbl_name  --列出索引信息
mysqlshow --status db_name  --列出数据库的描述性信息
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mysqldump可以让你看到create table语句(就想show create table语句一样),如:
mysqldump --no-data db_name [tbl_name] ...
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注意:在用mysqldump查看表结构时,一定要加上--no-data,否则你看到的将是数据库表里的数据。



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