1、查看当前有多少数据库
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| test |
| test_db |
| zxy |
+--------------------+
6 rows in set (0.00 sec)2、查看当前数据库
mysql> select database();
+------------+
| database() |
+------------+
| mysql |
+------------+
1 row in set (0.00 sec)
还可以使用status，不仅可以查看当前数据库，还可以直接看到数据库的编码
mysql> status;
--------------
mysql Ver 14.14 Distrib 5.6.41, for Linux (x86_64) using EditLine wrapper
Connection id: 4
Current database: mysql
Current user: root@
SSL: Not in use
Current pager: stdout
Using outfile: ''
Using delimiter: ;
Server version: 5.6.41 MySQL Community Server (GPL)
Protocol version: 10
Connection: Localhost via UNIX socket
Server characterset: latin1
Db characterset: latin1
Client characterset: utf8
Conn. characterset: utf8
UNIX socket: /var/lib/mysql/mysql.sock
Uptime: 4 hours 11 min 23 sec
Threads: 3 Questions: 357 Slow queries: 0 Opens: 34 Flush tables: 1 Open tables: 29 Queries per second avg: 0.023
--------------3、切换数据库
mysql> use zxy
Database changed
mysql> select database();
+------------+
| database() |
+------------+
| zxy |
+------------+
1 row in set (0.00 sec)
mysql> 4、查看数据库使用的端口号和字符集
mysql> show variables like 'port';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| port | 3306 |
+---------------+-------+
1 row in set (0.00 sec)
同理，你可以查看当前数据库的字符集
mysql> show variables like 'character%';
+--------------------------+----------------------------+
| Variable_name | Value |
+--------------------------+----------------------------+
| character_set_client | utf8 |
| character_set_connection | utf8 |
| character_set_database | latin1 |
| character_set_filesystem | binary |
| character_set_results | utf8 |
| character_set_server | latin1 |
| character_set_system | utf8 |
| character_sets_dir | /usr/share/mysql/charsets/ |
+--------------------------+----------------------------+
8 rows in set (0.00 sec)
mysql> 5、查看数据库的大小
mysql> use information_schema
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
mysql> select concat(round(sum(data_length)/(1024*1024),2) + round(sum(index_length)/(1024*1024),2),'MB') as 'DB Size' from tables where table_schema='zxy';
+---------+
| DB Size |
+---------+
| NULL |
+---------+
1 row in set (0.01 sec)6、查看当前的所有用户
mysql> select user,password,host from mysql.user;
+------+----------+-----------+
| user | password | host |
+------+----------+-----------+
| root | | localhost |
+------+----------+-----------+
1 row in set (0.00 sec)
7、查看当前数据库最大连接数
mysql> show variables like '%max_connections';
+-----------------+-------+
| Variable_name | Value |
+-----------------+-------+
| max_connections | 151 |
+-----------------+-------+
1 row in set (0.00 sec)
8、查看当前并发数
mysql> show status like 'Threads%';
+-------------------+-------+
| Variable_name | Value |
+-------------------+-------+
| Threads_cached | 0 |
| Threads_connected | 3 |
| Threads_created | 3 |
| Threads_running | 1 |
+-------------------+-------+
4 rows in set (0.00 sec)
Threads_cached : 代表当前此时此刻线程缓存中有多少空闲线程。
Threads_connected :代表当前已建立连接的数量，因为一个连接就需要一个线程，所以也可以看成当前被使用的线程数。
Threads_created :代表从最近一次服务启动，已创建线程的数量。
Threads_running :代表当前激活的（非睡眠状态）线程数。并不是代表正在使用的线程数，有时候连接已建立，但是连接处于sleep状态，这里相对应的线程也是sleep状态。9、查看当前数据文件的路径
mysql> show variables like '%datadir%';
+---------------+----------------------+
| Variable_name | Value |
+---------------+----------------------+
| datadir | /root/mysql/datadir/ |
+---------------+----------------------+
1 row in set (0.01 sec)