每日MySQL之002：MySQL server连接与查询

1 连接到 MySQL server

mysql命令是一个client MySQL Command-Line Tool 工具，它可以用来连接MySQL server，连接成功之后，会提供一个交互shell, 最常见的语法如下：

shell> mysql -h host -u user -p

其中-h 表示hostname， -u表示用户名，-p表示要输入密码：

db2a:~ # mysql -h localhost -u root -p

Enter password: ********

Welcome to the MySQL monitor.  Commands end with ; or \g.

Your MySQL connection id is 7

Server version: 5.7.19 MySQL Community Server (GPL)

Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its

affiliates. Other names may be trademarks of their respective

owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> 

2 开始查询

查询当前版本和日期，最后要以';'结尾：

mysql> select version(), current_date;

+-----------+--------------+

| version() | current_date |

+-----------+--------------+

| 5.7.19    | 2017-07-24   |

+-----------+--------------+

1 row in set (0.00 sec)

select语句不区分大小写；

mysql> SeLeCt vErSiOn(), current_DATE;

+-----------+--------------+

| vErSiOn() | current_DATE |

+-----------+--------------+

| 5.7.19    | 2017-07-24   |

+-----------+--------------+

1 row in set (0.00 sec)

可以作为简单的计算器：

mysql> select PI(),sin(PI()/4), (4+1)*5;

+----------+--------------------+---------+

| PI()     | sin(PI()/4)        | (4+1)*5 |

+----------+--------------------+---------+

| 3.141593 | 0.7071067811865475 |      25 |

+----------+--------------------+---------+

1 row in set (0.01 sec)

可以一行放两条SQL:

mysql> select version();select now();

+-----------+

| version() |

+-----------+

| 5.7.19    |

+-----------+

1 row in set (0.00 sec)

+---------------------+

| now()               |

+---------------------+

| 2017-07-24 15:06:02 |

+---------------------+

1 row in set (0.00 sec)

一条SQL也可以分行输入：

mysql> select

    -> user()

    -> ,

    -> current_date;

+----------------+--------------+

| user()         | current_date |

+----------------+--------------+

| root@localhost | 2017-07-24   |

+----------------+--------------+

1 row in set (0.01 sec)

输入的过程中，如果想要取消，可以输入\c

mysql> select 

    -> user()

    -> \c

mysql>