Home >Database >Mysql Tutorial >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 -proot mysqlshow: [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 xinxing mysqlshow: [Warning] Using a password on the command line interface can be insecure. Database: xinxing +--------+ | Tables | +--------+ | xin | +--------+ C:\Users\Administrator>mysqlshow -u root -proot --status xinxing mysqlshow: [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_f ree | Auto_increment | Create_time | Update_time | Check_time | Collation | Checksum | Cr eate_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 xin mysqldump: [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。。