注释：
以/**注释内容**/

mysql> /**列出所有的数据库**/ show databases; 
+--------------------+ 
| Database           | 
+--------------------+ 
| information_schema | 
| db_springcloud     | 
| mysql              | 
| performance_schema | 
| test               | 
| wordpress          | 
| xinyu              | 
| xinyu2             | 
| zabbix             | 
+--------------------+ 
9 rows in set (0.00 sec) 

   
    

###注释是从‘#’字符到行尾

mysql> #这里是注释，到行尾都是注释，所以后面的命令不执行 showdatabases; 
mysql>  

   
    

如果遇到很长的sql语句的话，在控制台为了阅读方便，我们可以使用\，使之继续输入；

mysql> show \ 
    -> databases; 
+--------------------+ 
| Database           | 
+--------------------+ 
| information_schema | 
| db_springcloud     | 
| mysql              | 
| performance_schema | 
| test               | 
| wordpress          | 
| xinyu              | 
| xinyu2             | 
| zabbix             | 
+--------------------+ 
9 rows in set (0.00 sec) 
mysql>
 

   
    

也支持正则like查询

mysql> show databases like '%inyu%'; 
+-------------------+ 
| Database (%inyu%) | 
+-------------------+ 
| xinyu             | 
| xinyu2            | 
+-------------------+ 
2 rows in set (0.00 sec) 

   
    

同理，show tables也支持，用from语法，可以少一步use 数据库

mysql> show tables from test; 
+----------------+ 
| Tables_in_test | 
+----------------+ 
| hbk            | 
+----------------+ 
1 row in set (0.00 sec) 
mysql> show tables from test like '%b%';
 
+----------------------+
 
| Tables_in_test (%b%) |
 
+----------------------+
 
| hbk                  |
 
+----------------------+
 
1 row in set (0.00 sec)
 

   
    

查看表定义，可以使用show create table 表名 \G
\G只是显示的格式更好看而已，也可以使用describe语法

mysql> use test; 
mysql> show create table hbk \G; 
*************************** 1. row *************************** 
       Table: hbk 
Create Table: CREATE TABLE `hbk` ( 
  `id` int(11) NOT NULL AUTO_INCREMENT, 
  `name` varchar(20) NOT NULL, 
  PRIMARY KEY (`id`) 
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=latin1 
1 row in set (0.00 sec) 
ERROR:
 
No query specified
 
mysql> describe hbk;
 
+-------+-------------+------+-----+---------+----------------+
 
| Field | Type        | Null | Key | Default | Extra          |
 
+-------+-------------+------+-----+---------+----------------+
 
| id    | int(11)     | NO   | PRI | NULL    | auto_increment |
 
| name  | varchar(20) | NO   |     | NULL    |                |
 
+-------+-------------+------+-----+---------+----------------+
 
2 rows in set (0.00 sec)
 
mysql> desc hbk;
 
+-------+-------------+------+-----+---------+----------------+
 
| Field | Type        | Null | Key | Default | Extra          |
 
+-------+-------------+------+-----+---------+----------------+
 
| id    | int(11)     | NO   | PRI | NULL    | auto_increment |
 
| name  | varchar(20) | NO   |     | NULL    |                |
 
+-------+-------------+------+-----+---------+----------------+
 
2 rows in set (0.01 sec)
 

   
    

知识点注意：
数据名的最大长度64字节
表名的最大长度64字节
列名的最大长度64字节
索引名的最大长度64字节
别名的最大长度255字节

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