辛星浅谈mysql中的元数据_MySQL

首先解释一下什么是元数据，所谓元数据，就是表示数据的数据，这些数据五花八门，总之，只要不是我们存储到数据库里的数据，大多都可以理解为元数据。那么我们如何来获取这些元数据呢？

总的来说，有三种思路，第一种，各种show，第二种，各种select，第三种，是mysql的命令行下的命令，不是sql语句。

我们首先看第一种，这里我列举一下大家比较熟悉的show语句的用法，其实咱们经常用show来查看信息，比如：

show databases;show tales;show create table 表名;show index from 表名;....等等

第二种就是通过select来从mysql数据库或者information_schema数据库中提取相关信息，比如可以从tables这个表里面的free_data字段来查看数据碎片的相关信息，这里我上一篇博文已经介绍过了，这里就不废话了。

第三种就是通过mysql自带的一些命令来查看，这个需要咱们的用户名和密码的，下面是我查看相应本文来源gaodai#ma#com搞*代#码9网#元数据的代码，希望能帮到您：

Microsoft Windows [版本 6.1.7601]版权所有 (c) 2009 Microsoft Corporation。保留所有权利。C:\Users\Administrator>mysqlshow -u root -prootmysqlshow: [Warning] Using a password on the command line interface can be insecure.+--------------------+|     Databases      |+--------------------+| information_schema || mysql              || performance_schema || test               || xinxing            |+--------------------+C:\Users\Administrator>mysqlshow -u root -proot xinxingmysqlshow: [Warning] Using a password on the command line interface can be insecure.Database: xinxing+--------+| Tables |+--------+| xin    |+--------+C:\Users\Administrator>mysqlshow -u root -proot --status xinxingmysqlshow: [Warning] Using a password on the command line interface can be insecure.Database: xinxing+------+--------+---------+------------+------+----------------+-------------+-------------------+--------------+-----------+----------------+---------------------+---------------------+---------------------+-----------------+----------+----------------+---------+| Name | Engine | Version | Row_format | Rows | Avg_row_length | Data_length | Max_data_length   | Index_length | Data_free | Auto_increment | Create_time         | Update_time         | Check_time          | Collation       | Checksum | Create_options | Comment |+------+--------+---------+------------+------+----------------+-------------+-------------------+--------------+-----------+----------------+---------------------+---------------------+---------------------+-----------------+----------+----------------+---------+| xin  | MyISAM | 10      | Fixed      | 3    | 121            | 363         | 34058472181989375 | 1024         | 0    |                | 2014-08-25 13:19:02 | 2014-08-25 13:41:25 | 2014-08-25 13:41:25 | utf8_general_ci |          |             |         |+------+--------+---------+------------+------+----------------+-------------+-------------------+--------------+-----------+----------------+---------------------+---------------------+---------------------+-----------------+----------+----------------+---------+C:\Users\Administrator>

下面是我用mysqldump来查看表结构的一些操作，希望对您有用：

C:\Users\Administrator>mysqldump -u root -proot --no-data xinxing xinmysqldump: [Warning] Using a password on the command line interface can be insecure.-- MySQL dump 10.13  Distrib 5.7.3-m13, for Win64 (x86_64)---- Host: localhost    Database: xinxing-- -------------------------------------------------------- Server version       5.7.3-m13/*!40101 SET @OLD_CHARACTER_SET_CLIENT=@@CHARACTER_SET_CLIENT */;/*!40101 SET @OLD_CHARACTER_SET_RESULTS=@@CHARACTER_SET_RESULTS */;/*!40101 SET @OLD_COLLATION_CONNECTION=@@COLLATION_CONNECTION */;/*!40101 SET NAMES utf8 */;/*!40103 SET @OLD_TIME_ZONE=@@TIME_ZONE */;/*!40103 SET TIME_ZONE='+00:00' */;/*!40014 SET @OLD_UNIQUE_CHECKS=@@UNIQUE_CHECKS, UNIQUE_CHECKS=0 */;/*!40014 SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0 */;/*!40101 SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE='NO_AUTO_VALUE_ON_ZERO' */;/*!40111 SET @OLD_SQL_NOTES=@@SQL_NOTES, SQL_NOTES=0 */;---- Table structure for table `xin`--DROP TABLE IF EXISTS `xin`;/*!40101 SET @saved_cs_client     = @@character_set_client */;/*!40101 SET character_set_client = utf8 */;CREATE TABLE `xin` (  `c` char(40) DEFAULT NULL) ENGINE=MyISAM DEFAULT CHARSET=utf8;/*!40101 SET character_set_client = @saved_cs_client */;/*!40103 SET TIME_ZONE=@OLD_TIME_ZONE */;/*!40101 SET SQL_MODE=@OLD_SQL_MODE */;/*!40014 SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS */;/*!40014 SET UNIQUE_CHECKS=@OLD_UNIQUE_CHECKS */;/*!40101 SET CHARACTER_SET_CLIENT=@OLD_CHARACTER_SET_CLIENT */;/*!40101 SET CHARACTER_SET_RESULTS=@OLD_CHARACTER_SET_RESULTS */;/*!40101 SET COLLATION_CONNECTION=@OLD_COLLATION_CONNECTION */;/*!40111 SET SQL_NOTES=@OLD_SQL_NOTES */;-- Dump completed on 2014-08-25 20:49:08

辛星，期待您的关注。。

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