-u // 指定用户名
-p // 指定密码
-P // 指定端口
-h // 指定主机名

mysql> help

For information about MySQL products and services, visit:
   http://www.mysql.com/
For developer information, including the MySQL Reference Manual, visit:
   http://dev.mysql.com/
To buy MySQL Enterprise support, training, or other products, visit:
   https://shop.mysql.com/

List of all MySQL commands:
Note that all text commands must be first on line and end with ';'
?         (?) Synonym for `help'.
clear     (c) Clear the current input statement.
connect   (
) Reconnect to the server. Optional arguments are db and host.
delimiter (d) Set statement delimiter.
ego       (G) Send command to mysql server, display result vertically.
exit      (q) Exit mysql. Same as quit.
go        (g) Send command to mysql server.
help      (h) Display this help.
notee     (	) Don't write into outfile.
print     (p) Print current command.
prompt    (R) Change your mysql prompt.
quit      (q) Quit mysql.
rehash    (#) Rebuild completion hash.
source    (.) Execute an SQL script file. Takes a file name as an argument.
status    (s) Get status information from the server.
system    (!) Execute a system shell command.
tee       (T) Set outfile [to_outfile]. Append everything into given outfile.
use       (u) Use another database. Takes database name as argument.
charset   (C) Switch to another charset. Might be needed for processing binlog with multi-byte charsets.
warnings  (W) Show warnings after every statement.
nowarning (w) Don't show warnings after every statement.
resetconnection(x) Clean session context.

For server side help, type 'help contents'

查询所有数据库：

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
4 rows in set (0.01 sec)

切换到某一个数据库：

mysql> use [db_name];
Database changed

查询当前选择的数据库中的所有可用表：

mysql> show tables;
mysql> show tables from [db_name]; // 查询指定数据库中的所有可用表
+-------------------+
| Tables_in_acgfate |
+-------------------+
| accounts          |
| users             |
+-------------------+
2 rows in set (0.01 sec)

查询指定表中的所有列：

mysql> show columns from [table];
+------------+------------------+------+-----+---------+----------------+
| Field      | Type             | Null | Key | Default | Extra          |
+------------+------------------+------+-----+---------+----------------+
| id         | bigint unsigned  | NO   | PRI | NULL    | auto_increment |
| created_at | datetime(3)      | YES  |     | NULL    |                |
| updated_at | datetime(3)      | YES  |     | NULL    |                |
| deleted_at | datetime(3)      | YES  | MUL | NULL    |                |
| username   | longtext         | YES  |     | NULL    |                |
| password   | longtext         | YES  |     | NULL    |                |
| nickname   | longtext         | YES  |     | NULL    |                |
| mail       | longtext         | YES  |     | NULL    |                |
| avatar     | longtext         | YES  |     | NULL    |                |
| gender     | longtext         | YES  |     | NULL    |                |
| level      | tinyint unsigned | YES  |     | NULL    |                |
| join_time  | datetime(3)      | YES  |     | NULL    |                |
| silence    | tinyint(1)       | YES  |     | NULL    |                |
+------------+------------------+------+-----+---------+----------------+
13 rows in set (0.01 sec)

数据操作

查询 简单查询 按列查询

SELECT [column] FROM [table];
SELECT [column1], [column2] FROM [table];
SELECT * FROM [table];

• 以上的简单查询语句得到的记录列表顺序是以数据底层的顺序为依据，而不是记录的先后顺序
  SQL 语句关键字不区分大小写
  SQL 语句中所有的空格会被忽略
  查询不同的行
  表中某些列的数据可能是存在重复的，使用DISTINCT关键字可以查询不重复的单列记录：

SELECT DISTINCT [column] FROM [table]

• 当指定多个列时，DISTINCT 会应用于所有的这些列，也就是多个列的唯一组合，如：

• 当存在多个NULL值时，会把其当作同名看待，最终只返回一个NULL

限制结果

使用LIMIT子句可以限定查询的范围，而不是查询整个表的记录：

SELECT [column] FROM [table] LIMIT 5; // 查询前5行
SELECT [column] FROM [table] LIMIT 5, 5 // 查询从第6行开始的5条记录

• 使用 LIMIT 查询得到的结果是按照记录顺序有序输出的
  LIMIT num1, num2中，num1 从 0 开始，因此 5 代表第六行
  当 LIMIT 指定的行数大于符合条件的记录数时，返回最大的记录条数
  限定表名

SELECT [table].[column] FROM [table]

排序查询

按指定列排序

SELECT [column1] FROM [table] ORDER BY [column2]
SELECT [column1] FROM [table] ORDER BY [column2] DESC // 按降序排序

• ORDER BY 默认升序排序
• 选择排序的列并不一定要显示
• 排序的规则（如 A 和 a 的大小）取决于数据库的设置，在字典排序中，A 被视为与 a 相同

按多个列排序

SELECT [column1] FROM [table] ORDER BY [column2], [column3]
SELECT [column1] FROM [table] ORDER BY [column2] DESC, [column3]

• 排序时会按照从左到右的顺序，首先按[column2]，排序，接着使用[column3]排序
• 可以将DESC放在指定列的后面让这一列降序排序