Mysql查询数据库连接状态及连接信息

Mysql查询数据库连接状态及连接信息

使用MySQL时，需要了解当前数据库的情况，例如当前的数据库大小、字符集、用户等等。下面总结了一些查看数据库相关信息的命令

1. 查看显示所有数据库

mysql> show databases;+--------------------+| Database           |+--------------------+| information_schema || INVOICE            || mysql              || performance_schema || test               |+--------------------+5 rows in set (0.00 sec) mysql> 

2. 查看当前使用的数据库

mysql> select database();+------------+| database() |+------------+| INVOICE    |+------------+1 row in set (0.00 sec) mysql> 

3. 查看数据库使用端口

mysql> show variables  like 'port';+---------------+-------+| Variable_name | Value |+---------------+-------+| port          | 3306  |+---------------+-------+1 row in set (0.00 sec)

4. 查看当前数据库大小

例如，我要查看INVOICE数据库的大小，那么可以通过下面SQL查看

mysql> use  information_schemaReading table information for completion of table and column namesYou can turn off this feature to get a quicker startup with -A Database changedmysql> 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='INVOICE';+-----------+| DB Size   |+-----------+| 7929.58MB |+-----------+1 row in set, 1 warning (0.00 sec)

5. 查看数据所占的空间大小

mysql> use information_schema;Reading table information for completion of table and column namesYou can turn off this feature to get a quicker startup with -A Database changedmysql> select concat(round(sum(data_length)/(1024*1024),2),'MB') as 'DB Size'    -> from tables    -> where table_schema='INVOICE';+-----------+| DB Size   |+-----------+| 6430.26MB |+-----------+1 row in set, 1 warning (0.00 sec) mysql> 

6. 查看索引所占的空间大小

mysql> select concat(round(sum(index_length)/(1024*1024),2),'MB') as 'DB Size'     -> from tables     -> where table_schema='INVOICE';+-----------+| DB Size   |+-----------+| 1499.32MB |+-----------+1 row in set, 1 warning (0.13 sec) mysql> 

7. 查看数据库编码

mysql> show variables like 'character%';+--------------------------+----------------------------+| Variable_name            | Value                      |+--------------------------+----------------------------+| character_set_client     | utf8                       || character_set_connection | utf8                       || character_set_database   | utf8                       || 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)

character_set_client 为客户端编码方式；

character_set_connection 为建立连接使用的编码；

character_set_database 为数据库的编码；

character_set_results 为结果集的编码；

character_set_server 为数据库服务器的编码；

只要保证以上采用的编码方式一样，就不会出现乱码问题。

mysql> show variables like 'collation%';+----------------------+-------------------+| Variable_name        | Value             |+----------------------+-------------------+| collation_connection | utf8_general_ci   || collation_database   | utf8_general_ci   || collation_server     | latin1_swedish_ci |+----------------------+-------------------+3 rows in set (0.00 sec)

status也可以查看数据库的编码

mysql> status;--------------mysql  Ver 14.14 Distrib 5.6.20, for Linux (x86_64) using  EditLine wrapper Connection id:          1Current database:       INVOICECurrent user:           root@localhostSSL:                    Not in useCurrent pager:          stdoutUsing outfile:          ''Using delimiter:        ;Server version:         5.6.20-enterprise-commercial-advanced MySQL Enterprise Server - Advanced Edition (Commercial)Protocol version:       10Connection:             Localhost via UNIX socketServer characterset:    latin1Db     characterset:    latin1Client characterset:    utf8Conn.  characterset:    utf8UNIX socket:            /var/lib/mysql/mysql.sockUptime:                 5 hours 18 min 51 sec Threads: 1  Questions: 10884  Slow queries: 0  Opens: 650  Flush tables: 1  Open tables: 268  Queries per second avg: 0.568--------------mysql> 

8. 查看数据库的表信息

mysql> show tables;+---------------------------------------+| Tables_in_information_schema          |+---------------------------------------+| CHARACTER_SETS                        || COLLATIONS|| COLLATION_CHARACTER_SET_APPLICABILITY || COLUMNS   || COLUMN_PRIVILEGES                     || ENGINES   || EVENTS    || FILES     || GLOBAL_STATUS                         || GLOBAL_VARIABLES                      || KEY_COLUMN_USAGE                      || OPTIMIZER_TRACE                       || PARAMETERS|| PARTITIONS|| PLUGINS   || PROCESSLIST                           || PROFILING || REFERENTIAL_CONSTRAINTS               || ROUTINES  || SCHEMATA  || SCHEMA_PRIVILEGES                     || SESSION_STATUS                        || SESSION_VARIABLES                     || STATISTICS|| TABLES    || TABLESPACES                           || TABLE_CONSTRAINTS                     || TABLE_PRIVILEGES                      || TRIGGERS  || USER_PRIVILEGES                       || VIEWS     || INNODB_LOCKS                          || INNODB_TRX|| INNODB_SYS_DATAFILES                  || INNODB_LOCK_WAITS                     || INNODB_SYS_TABLESTATS                 || INNODB_CMP|| INNODB_METRICS                        || INNODB_CMP_RESET                      || INNODB_CMP_PER_INDEX                  || INNODB_CMPMEM_RESET                   || INNODB_FT_DELETED                     || INNODB_BUFFER_PAGE_LRU                || INNODB_SYS_FOREIGN                    || INNODB_SYS_COLUMNS                    || INNODB_SYS_INDEXES                    || INNODB_FT_DEFAULT_STOPWORD            || INNODB_SYS_FIELDS                     || INNODB_CMP_PER_INDEX_RESET            || INNODB_BUFFER_PAGE                    || INNODB_CMPMEM                         || INNODB_FT_INDEX_TABLE                 || INNODB_FT_BEING_DELETED               || INNODB_SYS_TABLESPACES                || INNODB_FT_INDEX_CACHE                 || INNODB_SYS_FOREIGN_COLS               || INNODB_SYS_TABLES                     || INNODB_BUFFER_POOL_STATS              || INNODB_FT_CONFIG                      |+---------------------------------------+59 rows in set (0.00 sec)

或者使用下面SQL语句查看某个数据库的表信息。

select * from information_schema.tables where table_schema=‘databasename’;

查看某种具体表的信息

select * from information_schema.tables where table_name =‘table_name’

9. ：查看数据库的所有用户信息

mysql>  select distinct concat('user: ''',user,'''@''',host,''';') as query from mysql.user;+-------------------------------------+| query   |+-------------------------------------+| user: 'root'@'127.0.0.1';           || user: 'root'@'::1';                 || user: 'root'@'gettesx20.test.com'; || user: 'root'@'localhost';           |+-------------------------------------+4 rows in set (0.00 sec) mysql> 

10. 查看某个具体用户的权限

mysql> show grants for 'root'@'localhost';+---------------------------------------------------------------------------------------------------------------------------------+| Grants for root@localhost                          |+---------------------------------------------------------------------------------------------------------------------------------+| GRANT ALL PRIVILEGES ON *.* TO 'root'@'localhost' IDENTIFIED BY PASSWORD '*C7B1594FD74578DA3A92A61720AC67C6DBE6FC23' WITH GRANT OPTION || GRANT PROXY ON ''@'' TO 'root'@'localhost' WITH GRANT OPTION                   |+---------------------------------------------------------------------------------------------------------------------------------+2 rows in set (0.00 sec)

11. 查看数据库的最大连接数

mysql>  show variables like '%max_connections%';+-----------------+-------+| Variable_name   | Value |+-----------------+-------+| max_connections | 151   |+-----------------+-------+1 row in set (0.00 sec) mysql> 

12. 查看数据库当前连接数，并发数。

mysql> show status like 'Threads%';+-------------------+-------+| Variable_name     | Value |+-------------------+-------+| Threads_cached    | 0     || Threads_connected | 1     || Threads_created   | 1     || 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。

13. 查看数据文件存放路径

mysql> show variables like '%datadir%';+---------------+-------------------+| Variable_name | Value             |+---------------+-------------------+| datadir       | /mysqldata/mysql/ |+---------------+-------------------+1 row in set (0.00 sec) mysql> 

来源地址：https://blog.csdn.net/weixin_50998273/article/details/128639199