MySQL用很多常用的内置变量，掌握这些内置变量后对于我们快速获取当前MySQL的配置有很大帮助，下面就来列举几个常用的变量。

查看当前MySQL版本号信息。show variables like 'version';

MariaDB [(none)]> show variables like 'version';

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

| Variable_name | Value |

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

| version | 5.5.60-MariaDB |

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

1 row in set (0.00 sec)

查看当前MySQL服务监听的端口号信息。show variables like 'port';

MariaDB [(none)]> show variables like 'port';

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

| Variable_name | Value |

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

| port | 3306 |

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

1 row in set (0.00 sec)

查看当前MySQL数据的默认存储路径信息。show variables like 'datadir';

MariaDB [(none)]> show variables like 'datadir';

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

| Variable_name | Value |

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

| datadir | /var/lib/mysql/ |

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

1 row in set (0.00 sec)

查看当前MySQL使用的引擎信息。show variables like 'storage_engine';

MariaDB [(none)]> show variables like 'storage_engine';

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

| Variable_name | Value |

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

| storage_engine | InnoDB |

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

1 row in set (0.01 sec)

查看当前MySQL的最大连接数信息。show variables like 'max_connections';

MariaDB [(none)]> show variables like 'max_connections';

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

| Variable_name | Value |

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

| max_connections | 151 |

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

1 row in set (0.00 sec)

修改max_connectionis变量值：

MariaDB [(none)]> set global max_connections=65535;

Query OK, 0 rows affected (0.00 sec)

MariaDB [(none)]> show variables like 'max_connections';

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

| Variable_name | Value |

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

| max_connections | 65535 |

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

1 row in set (0.00 sec)

掌握一些必要的变量后发现在使用过程中修改，是不用重启MySQL服务的，这样我们可以先进入MySQL将最大连接数进行修改，后续加入到配置文件中，选择维护时间将MySQL重启，配置就可以永久生效了。