mysql中使用show variables同时查询多个参数值?show variables的使用?

需求描述:

　　今天在查mysq关于连接数的问题,想要通过一个show variables命令同时查出来多个值.在此记录下.

操作过程:

1.通过show variables语句的like可以匹配多个值或者某个值

mysql> show variables like 'max_connections';   #这里默认的就是对Variable_name进行匹配,这里是准确匹配.
+-----------------+-------+
| Variable_name   | Value |
+-----------------+-------+
| max_connections | 151   |
+-----------------+-------+
1 row in set (0.01 sec)

mysql> show variables like 'socket';
+---------------+-----------------+
| Variable_name | Value           |
+---------------+-----------------+
| socket        | /tmp/mysql.sock |
+---------------+-----------------+
1 row in set (0.00 sec)

2.通过%通配符进行匹配

mysql> show variables like '%connec%';      #通过百分号(%)这个通配符进行匹配,可以匹配多项.
+-----------------------------------------------+-------------------+
| Variable_name                                 | Value             |
+-----------------------------------------------+-------------------+
| character_set_connection                      | latin1            |
| collation_connection                          | latin1_swedish_ci |
| connect_timeout                               | 10                |
| disconnect_on_expired_password                | ON                |
| init_connect                                  |                   |
| max_connect_errors                            | 100               |
| max_connections                               | 151               |
| max_user_connections                          | 0                 |
| performance_schema_session_connect_attrs_size | 512               |
+-----------------------------------------------+-------------------+
9 rows in set (0.00 sec)

mysql> show variables like 'innodb_thread%';  #%通配符在结束处.
+---------------------------+-------+
| Variable_name             | Value |
+---------------------------+-------+
| innodb_thread_concurrency | 0     |
| innodb_thread_sleep_delay | 10000 |
+---------------------------+-------+
2 rows in set (0.00 sec)

mysql> show variables like '%version';  #%通配符在开始处.
+------------------+---------------+
| Variable_name    | Value         |
+------------------+---------------+
| innodb_version   | 5.7.21        |
| protocol_version | 10            |
| tls_version      | TLSv1,TLSv1.1 |
| version          | 5.7.21-log    |
+------------------+---------------+
4 rows in set (0.00 sec)

3.使用where子句进行匹配查询

mysql> show variables where variable_name = 'version';
+---------------+------------+
| Variable_name | Value      |
+---------------+------------+
| version       | 5.7.21-log |
+---------------+------------+
1 row in set (0.01 sec)

mysql> show variables where variable_name in ('version','innodb_version');
+----------------+------------+
| Variable_name  | Value      |
+----------------+------------+
| innodb_version | 5.7.21     |
| version        | 5.7.21-log |
+----------------+------------+
2 rows in set (0.00 sec)

mysql> show variables where value like '5.7%';
+----------------+------------+
| Variable_name  | Value      |
+----------------+------------+
| innodb_version | 5.7.21     |
| version        | 5.7.21-log |
+----------------+------------+
2 rows in set (0.00 sec)

mysql> show variables where variable_name = 'version' and value = '5.7';
Empty set (0.00 sec)

mysql> show variables where variable_name = 'version' and value like '5.7%';
+---------------+------------+
| Variable_name | Value      |
+---------------+------------+
| version       | 5.7.21-log |
+---------------+------------+
1 row in set (0.00 sec)

备注:使用where子句的方式就和在SQL语句中使用where的方式是一样的.

4.使用_(下划线)匹配单个字符及将下划线当做普通字符使用

mysql> show variables like 'versio_\_c%';   #第一个是通配符,匹配一个字符,第二个下划线当做普通字符使用,所以在前面加上了转义字符\,将其转义为普通字符.
+-------------------------+------------------------------+
| Variable_name           | Value                        |
+-------------------------+------------------------------+
| version_comment         | MySQL Community Server (GPL) |
| version_compile_machine | x86_64                       |
| version_compile_os      | linux-glibc2.12              |
+-------------------------+------------------------------+
3 rows in set (0.00 sec)

show variables语法:

SHOW [GLOBAL | SESSION] VARIABLES
    [LIKE 'pattern' | WHERE expr]

小结:

• show variables主要是用来查看系统变量的值.
• 执行SHOW VARIABLES命令不需要任何权限,只要求能够连接到服务器就可以.
• 使用like语句表示用variable_name进行匹配.
• %百分号通配符可以用在匹配模式中的任何位置

文档创建时间:2018年7月17日11:33:27