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本文丸趣 TV 小编为大家详细介绍“Mysql 怎么查询数据库连接状态及连接信息”，内容详细，步骤清晰，细节处理妥当，希望这篇“Mysql 怎么查询数据库连接状态及连接信息”文章能帮助大家解决疑惑，下面跟着丸趣 TV 小编的思路慢慢深入，一起来学习新知识吧。
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查看当前使用的数据库
mysql select database();
+------------+
| database() |
+------------+
| INVOICE |
+------------+
1 row in set (0.00 sec)
mysql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)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_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= INVOICE
+-----------+
| DB Size |
+-----------+
| 7929.58MB |
+-----------+
1 row in set, 1 warning (0.00 sec)查看数据所占的空间大小
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), MB ) as DB Size
- from tables
- where table_schema= INVOICE
+-----------+
| DB Size |
+-----------+
| 6430.26MB |
+-----------+
1 row in set, 1 warning (0.00 sec)
mysql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: 1
Current database: INVOICE
Current user: root@localhost
SSL: Not in use
Current pager: stdout
Using outfile:
Using delimiter: ;
Server version: 5.6.20-enterprise-commercial-advanced MySQL Enterprise Server - Advanced Edition (Commercial)
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: 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)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。
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)
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