MySQL数据库(9)----从命令行获取元数据

1.　　mysqlshow 命令提供的信息与某些 SHOW 语句很相似，因此可以从命令行提示符获取数据库和表的信息。

(i)列出服务器所管理的数据库：

root@javis:~$ mysqlshow -p -uroot
Enter password: 
+--------------------+
|     Databases      |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sampdb             |
| test               |
+--------------------+

(ii)列出数据库里的表：

root@javis:~$ mysqlshow -p -uroot sampdb
Enter password: 
Database: sampdb
+-------------+
|   Tables    |
+-------------+
| absence     |
| grade_event |
| member      |
| mytable     |
| president   |
| score       |
| student     |
+-------------+

(iii) 显示表里的列信息：

root@javis:~$ mysqlshow -p -uroot sampdb student
Enter password: 
Database: sampdb  Table: student
+------------+------------------+-----------------+------+-----+---------+----------------+---------------------------------+---------+
| Field      | Type             | Collation       | Null | Key | Default | Extra          | Privileges                      | Comment |
+------------+------------------+-----------------+------+-----+---------+----------------+---------------------------------+---------+
| name       | varchar(20)      | utf8_general_ci | NO   |     |         |                | select,insert,update,references |         |
| sex        | enum('F','M')    | utf8_general_ci | NO   |     |         |                | select,insert,update,references |         |
| student_id | int(10) unsigned |                 | NO   | PRI |         | auto_increment | select,insert,update,references |         |
+------------+------------------+-----------------+------+-----+---------+----------------+---------------------------------+---------+

(iv) 显示表里的索引信息：

root@javis:~$ mysqlshow -p -uroot --keys sampdb student
Enter password: 
Database: sampdb  Table: student
+------------+------------------+-----------------+------+-----+---------+----------------+---------------------------------+---------+
| Field      | Type             | Collation       | Null | Key | Default | Extra          | Privileges                      | Comment |
+------------+------------------+-----------------+------+-----+---------+----------------+---------------------------------+---------+
| name       | varchar(20)      | utf8_general_ci | NO   |     |         |                | select,insert,update,references |         |
| sex        | enum('F','M')    | utf8_general_ci | NO   |     |         |                | select,insert,update,references |         |
| student_id | int(10) unsigned |                 | NO   | PRI |         | auto_increment | select,insert,update,references |         |
+------------+------------------+-----------------+------+-----+---------+----------------+---------------------------------+---------+
+---------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| Table   | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+---------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| student | 0          | PRIMARY  | 1            | student_id  | A         | 6           |          |        |      | BTREE      |         |               |
+---------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+

(v) 显示数据库里所有表的描述性信息：

root@javis:~$ mysqlshow -p -uroot --status sampdb
Enter password: 
Database: sampdb
+-------------+--------+---------+------------+------+----------------+-------------+-----------------+--------------+-----------+----------------+---------------------+-------------+------------+-----------------+----------+----------------+---------+
| 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 |
+-------------+--------+---------+------------+------+----------------+-------------+-----------------+--------------+-----------+----------------+---------------------+-------------+------------+-----------------+----------+----------------+---------+
| absence     | InnoDB | 10      | Compact    | 0    | 0              | 16384       | 0               | 0            | 0         |                | 2016-07-17 11:49:27 |             |            | utf8_general_ci |          |                |         |
| grade_event | InnoDB | 10      | Compact    | 0    | 0              | 16384       | 0               | 0            | 0         | 2              | 2016-07-17 11:44:18 |             |            | utf8_general_ci |          |                |         |
| member      | InnoDB | 10      | Compact    | 0    | 0              | 16384       | 0               | 0            | 0         | 1              | 2016-07-17 10:37:29 |             |            | utf8_general_ci |          |                |         |
| mytable     | InnoDB | 10      | Compact    | 0    | 0              | 16384       | 0               | 0            | 0         | 1              | 2016-07-26 20:48:29 |             |            | utf8_general_ci |          |                |         |
| president   | InnoDB | 10      | Compact    | 0    | 0              | 16384       | 0               | 0            | 0         |                | 2016-07-17 10:20:49 |             |            | utf8_general_ci |          |                |         |
| score       | InnoDB | 10      | Compact    | 0    | 0              | 16384       | 0               | 16384        | 0         |                | 2016-07-17 11:47:25 |             |            | utf8_general_ci |          |                |         |
| student     | InnoDB | 10      | Compact    | 6    | 2730           | 16384       | 0               | 0            | 0         | 10             | 2016-07-17 11:39:17 |             |            | utf8_general_ci |          |                |         |
+-------------+--------+---------+------------+------+----------------+-------------+-----------------+--------------+-----------+----------------+---------------------+-------------+------------+-----------------+----------+----------------+---------+

2. 客户端程序 mysqldump 能够让用户看到CREATE TABLE 语句 (与 SHOW CREATE TABLE 语句很像) 所定义的表结构。

(i) 如果使用 mysqldump 来查看表结构，切记要加上 --no-data 选项，否则看到的内容将是表里的数据

root@javis:~$ mysqldump -p -uroot --no-data sampdb
Enter password: 
-- MySQL dump 10.13  Distrib 5.6.31, for Linux (x86_64)
--
-- Host: localhost    Database: sampdb
-- ------------------------------------------------------
-- Server version    5.6.31

/*!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 `absence`
--

DROP TABLE IF EXISTS `absence`;
/*!40101 SET @saved_cs_client     = @@character_set_client */;
/*!40101 SET character_set_client = utf8 */;
CREATE TABLE `absence` (
  `student_id` int(10) unsigned NOT NULL,
  `date` date NOT NULL,
  PRIMARY KEY (`student_id`,`date`),
  CONSTRAINT `absence_ibfk_1` FOREIGN KEY (`student_id`) REFERENCES `student` (`student_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
/*!40101 SET character_set_client = @saved_cs_client */;

......以下省略......

　　如果指定了数据库的名字，而没有给出任何表名，那么 mysqldump 将把该数据库里所有表的结构显示出来。否则，它将只会显示那些通过名字指定的那些表的信息。

　　在使用 mysqlshow 和 mysqldump 时，记得要指定必要的连接参数，如 --host、--usr 或 --password。