MySQL 实用技巧

概述：

　　MySQL有许多实用的技巧，利用这些技巧能提高工作的效率，减少一些不必要的麻烦。以下是几个我在MySQL日常维护从常用的技巧。

一、prompt 命令

功能：设置mysql客户端提示符
说明：默认使用mysql命令行登录MySQL服务器后只会有[mysql>]的提示符，利用prompt命令则可以修改默认提示符，有利于数据库的维护，也能有效的防止误操作的发生。
用法：可在配置文件中配置，也可在命令行手动设定，写法有些许不同，详细参数说明如下，也可访问官方文档查看细节，链接如下：
http://dev.mysql.com/doc/refman/5.7/en/mysql-commands.html

详细选项说明：(红色为常用选项)

Option	Description
\C	The current connection identifier (MySQL 5.7.6 and up)
\c	A counter that increments for each statement you issue
\D	The full current date
\d	The default database
\h	The server host
\l	The current delimiter
\m	Minutes of the current time
\n	A newline character
\O	The current month in three-letter format (Jan, Feb, …)
\o	The current month in numeric format
\P	am/pm
\p	The current TCP/IP port or socket file
\R	The current time, in 24-hour military time (0–23)
\r	The current time, standard 12-hour time (1–12)
\S	Semicolon
\s	Seconds of the current time
\t	A tab character
\U	Your full user_name@host_name account name
\u	Your user name
\v	The server version
\w	The current day of the week in three-letter format (Mon, Tue, …)
\Y	The current year, four digits
\y	The current year, two digits
\_	A space
\	A space (a space follows the backslash)
\'	Single quote
\"	Double quote
\\	A literal “\” backslash character
\x	x, for any “x” not listed above

以下为配置示例：

1、在my.cnf配置文件[client]部分中增加以下配置
prompt="[\\r:\\m:\\s](\\U)[\\d] > "     -- 在配置文件中配置都需要用\对配置的参数进行转义

[root@manager ~]# mysql -p
Enter password: 
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 15
Server version: 5.7.10-log MySQL Community Server (GPL)
Copyright (c) 2000, 2015, 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.

[03:11:57](root@localhost)[(none)] >　　-- 显示时间 + 登录用户 + 当前使用的数据库(未使用则为none)
[03:15:40](root@localhost)[test] >

2、在mysql客户端内直接配置

mysql>prompt [\r:\m:\s](\U)[\d] >　　　　
PROMPT set to '[\r:\m:\s](\U)[\d] >'
[03:22:31](root@localhost)[(none)] >   -- 显示时间 + 登录用户 + 当前使用的数据库

[03:22:31](root@localhost)[(none)] >prompt (\U)[\d] >
PROMPT set to '(\U)[\d] >'
(root@localhost)[(none)] >             -- 只显示 登录用户 + 当前使用的数据库

二、tee/notee命令

功能：tee实现将命令行中的输入输出结果保存到文本文件中,使用该命令能方便的将命令进行日志记录。 
用法：tee /tmp/command.log

以下为使用示例：

[03:43:49](root@localhost)[(none)] > tee /tmp/command.log    -- 设置将输出的结果保存到文件中
Logging to file '/tmp/command.log'
[03:44:02](root@localhost)[(none)] > show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| paralleldb         |
| performance_schema |
| web                |
+--------------------+
10 rows in set (0.00 sec)

[03:44:18](root@localhost)[(none)] > system cat /tmp/command.log    -- 通过system 命令查看系统文件内容与数据库中内容一致
[03:44:02](root@localhost)[(none)] > show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| paralleldb         |
| performance_schema |
| web                |
+--------------------+
10 rows in set (0.00 sec)

[03:46:55](root@localhost)[(none)] > notee         -- 使用notee可结束文件的输出
Outfile disabled.

三、pager less/pager命令

功能：实现返回结果页面的分页显示，类似于Linux less 命令，可对分页进行上下翻页，搜索等操作，对返回结果过长很方便，如使用show engine innodb status命令时。
用法：
pager less -i   表示设置页面分页显示，-i表示不区分大小写，在搜索时十分实用。
pager　　　　　　 直接输入pager表示恢复默认值，也就是不分页显示。
示例：略，可自行测试效果

四、concat函数

功能：concat函数能对查询返回的结果进行拼接
用法：concat(s1,s2,...sn)
常用场景：批量生成对数据库的相关修改语句或导出语句
以下为具体示例：

1、批量生成将test数据库中所有表导出为.txt或csv文本的命令
-- 注意需要对单引号用反斜杠(\)进行转义

[04:06:57](root@localhost)[(none)] > select concat('select * into outfile \'/tmp/',table_name,'.csv\' from ',table_schema,'.',table_name,';') 
from information_schema.tables where  table_schema='test';
+---------------------------------------------------------------------------------------------------+
| concat('select * into outfile \'/tmp/',table_name,'.csv\' from ',table_schema,'.',table_name,';') |
+---------------------------------------------------------------------------------------------------+
| select * into outfile '/tmp/address.csv' from test.address;                                       |
| select * into outfile '/tmp/address1.csv' from test.address1;                                     |
| select * into outfile '/tmp/clone_t.csv' from test.clone_t;                                       |
| select * into outfile '/tmp/lock_test.csv' from test.lock_test;                                   |
| select * into outfile '/tmp/query_history.csv' from test.query_history;                           |
| select * into outfile '/tmp/query_review.csv' from test.query_review;                             |
| select * into outfile '/tmp/ram.csv' from test.ram;                                               |
| select * into outfile '/tmp/t.csv' from test.t;                                                   |
| select * into outfile '/tmp/t1.csv' from test.t1;                                                 |
| select * into outfile '/tmp/t2.csv' from test.t2;                                                 |
| select * into outfile '/tmp/t3.csv' from test.t3;                                                 |
| select * into outfile '/tmp/z.csv' from test.z;                                                   |
+---------------------------------------------------------------------------------------------------+

当需要对数据库的表进行批量操作时，通过这种方式批量生成语句能大大提高效率

2、去除结果的虚线框并将结果输出到文件中
-- 通常我们需要将生成的语句保存到一个文件中，并且运行，这时就需要配合tee命令以及mysql客户端的参数了
mysql --skip-column-names --silent  (简写为 mysql -ss)能以静默方式登录MySQL服务器并不显示输出结果的虚线框
tee  /tmp/export.sql　　　　 将执行的结果保存到文件中

[root@manager ~]# mysql -uroot -p -ss      -- 使用静默方式登录数据库
Enter password: 
[04:18:55](root@localhost)[(none)] > tee /tmp/export.sql     -- 将结果保存到外部文件中
Logging to file '/tmp/export.sql'
[04:19:04](root@localhost)[(none)] > select concat('select * into outfile \'/tmp/',table_name,'.csv\' from ',table_schema,'.',table_name,';') 
from information_schema.tables where  table_schema='test';
-- 可以看到输出的结果没有虚线框
select * into outfile '/tmp/address.csv' from test.address;
select * into outfile '/tmp/address1.csv' from test.address1;
select * into outfile '/tmp/clone_t.csv' from test.clone_t;
select * into outfile '/tmp/lock_test.csv' from test.lock_test;
select * into outfile '/tmp/query_history.csv' from test.query_history;
select * into outfile '/tmp/query_review.csv' from test.query_review;
select * into outfile '/tmp/ram.csv' from test.ram;
select * into outfile '/tmp/t.csv' from test.t;
select * into outfile '/tmp/t1.csv' from test.t1;
select * into outfile '/tmp/t2.csv' from test.t2;
select * into outfile '/tmp/t3.csv' from test.t3;
select * into outfile '/tmp/z.csv' from test.z;
[04:19:08](root@localhost)[(none)] > exit

-- 查看tee输出文件中的内容
[root@manager ~]# cat /tmp/export.sql 
[04:19:04](root@localhost)[(none)] > select concat('select * into outfile \'/tmp/',table_name,'.csv\' from ',table_schema,'.',table_name,';') from information_schema.tables where  table_schema='test';
select * into outfile '/tmp/address.csv' from test.address;
select * into outfile '/tmp/address1.csv' from test.address1;
select * into outfile '/tmp/clone_t.csv' from test.clone_t;
select * into outfile '/tmp/lock_test.csv' from test.lock_test;
select * into outfile '/tmp/query_history.csv' from test.query_history;
select * into outfile '/tmp/query_review.csv' from test.query_review;
select * into outfile '/tmp/ram.csv' from test.ram;
select * into outfile '/tmp/t.csv' from test.t;
select * into outfile '/tmp/t1.csv' from test.t1;
select * into outfile '/tmp/t2.csv' from test.t2;
select * into outfile '/tmp/t3.csv' from test.t3;
select * into outfile '/tmp/z.csv' from test.z;
[04:19:08](root@localhost)[(none)] > exit
-- 文件内容记录了所有的操作及输出的结果，可以编辑文件，将文件头的查询语句及文件尾的退出语句删除，则完成了一个将数据库导出成文本文件的的脚本。