MySQL之information_schema数据库详细讲解
时间：2023-01-07 09:28:27|栏目：Mysql|点击： 次
1. 概述
information_schema 数据库跟 performance_schema 一样，都是 MySQL 自带的信息数据库。其中 performance_schema 用于性能分析，而 information_schema 用于存储数据库元数据(关于数据的数据)，例如数据库名、表名、列的数据类型、访问权限等。
information_schema 中的表实际上是视图，而不是基本表，因此，文件系统上没有与之相关的文件。
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> 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_FT_CONFIG | | INNODB_SYS_VIRTUAL | | INNODB_CMP | | INNODB_FT_BEING_DELETED | | INNODB_CMP_RESET | | INNODB_CMP_PER_INDEX | | INNODB_CMPMEM_RESET | | INNODB_FT_DELETED | | INNODB_BUFFER_PAGE_LRU | | INNODB_LOCK_WAITS | | INNODB_TEMP_TABLE_INFO | | INNODB_SYS_INDEXES | | INNODB_SYS_TABLES | | INNODB_SYS_FIELDS | | INNODB_CMP_PER_INDEX_RESET | | INNODB_BUFFER_PAGE | | INNODB_FT_DEFAULT_STOPWORD | | INNODB_FT_INDEX_TABLE | | INNODB_FT_INDEX_CACHE | | INNODB_SYS_TABLESPACES | | INNODB_METRICS | | INNODB_SYS_FOREIGN_COLS | | INNODB_CMPMEM | | INNODB_BUFFER_POOL_STATS | | INNODB_SYS_COLUMNS | | INNODB_SYS_FOREIGN | | INNODB_SYS_TABLESTATS | +---------------------------------------+ 61 rows in set (0.00 sec)
2. information_schema 库中常用的表
CHARACTER_SETS 表
提供了 mysql 可用字符集的信息。SHOW CHARACTER SET; 命令从这个表获取结果。
mysql> SHOW CHARACTER SET; +----------+---------------------------------+---------------------+--------+ | Charset | Description | Default collation | Maxlen | +----------+---------------------------------+---------------------+--------+ | big5 | Big5 Traditional Chinese | big5_chinese_ci | 2 | | dec8 | DEC West European | dec8_swedish_ci | 1 | | cp850 | DOS West European | cp850_general_ci | 1 | ... | eucjpms | UJIS for Windows Japanese | eucjpms_japanese_ci | 3 | | gb18030 | China National Standard GB18030 | gb18030_chinese_ci | 4 | +----------+---------------------------------+---------------------+--------+ 41 rows in set (0.07 sec) mysql> SELECT * FROM CHARACTER_SETS; +--------------------+----------------------+---------------------------------+--------+ | CHARACTER_SET_NAME | DEFAULT_COLLATE_NAME | DESCRIPTION | MAXLEN | +--------------------+----------------------+---------------------------------+--------+ | big5 | big5_chinese_ci | Big5 Traditional Chinese | 2 | | dec8 | dec8_swedish_ci | DEC West European | 1 | | cp850 | cp850_general_ci | DOS West European | 1 | ... | eucjpms | eucjpms_japanese_ci | UJIS for Windows Japanese | 3 | | gb18030 | gb18030_chinese_ci | China National Standard GB18030 | 4 | +--------------------+----------------------+---------------------------------+--------+ 41 rows in set (0.00 sec)
SCHEMATA 表
当前 mysql 实例中所有数据库的信息。SHOW DATABASES; 命令从这个表获取数据。
mysql> SELECT * FROM SCHEMATA; +--------------+--------------------+----------------------------+------------------------+----------+ | CATALOG_NAME | SCHEMA_NAME | DEFAULT_CHARACTER_SET_NAME | DEFAULT_COLLATION_NAME | SQL_PATH | +--------------+--------------------+----------------------------+------------------------+----------+ | def | information_schema | utf8 | utf8_general_ci | NULL | | def | mysql | latin1 | latin1_swedish_ci | NULL | | def | performance_schema | utf8 | utf8_general_ci | NULL | | def | sys | utf8 | utf8_general_ci | NULL | | def | test | utf8 | utf8_unicode_ci | NULL | +--------------+--------------------+----------------------------+------------------------+----------+ 10 rows in set (0.00 sec) mysql> show databases; +--------------------+ | Database | +--------------------+ | information_schema | | mysql | | performance_schema | | sys | | test | +--------------------+ 10 rows in set (0.00 sec)
TABLES 表
存储数据库中的表信息（包括视图），包括表属于哪个数据库，表的类型、存储引擎、创建时间等信息。SHOW TABLES FROM XX; 命令从这个表获取结果。
mysql> SELECT * FROM TABLES; +---------------+--------------------+------------------------------------------------------+-------------+--------------------+---------+------------+------------+----------------+-------------+--------------------+--------------+-----------+----------------+---------------------+---------------------+---------------------+-------------------+----------+--------------------+--------------------------------------------+ | TABLE_CATALOG | TABLE_SCHEMA | TABLE_NAME | TABLE_TYPE | ENGINE | VERSION | ROW_FORMAT | TABLE_ROWS | AVG_ROW_LENGTH | DATA_LENGTH | MAX_DATA_LENGTH | INDEX_LENGTH | DATA_FREE | AUTO_INCREMENT | CREATE_TIME | UPDATE_TIME | CHECK_TIME | TABLE_COLLATION | CHECKSUM | CREATE_OPTIONS | TABLE_COMMENT | +---------------+--------------------+------------------------------------------------------+-------------+--------------------+---------+------------+------------+----------------+-------------+--------------------+--------------+-----------+----------------+---------------------+---------------------+---------------------+-------------------+----------+--------------------+--------------------------------------------+ | def | information_schema | CHARACTER_SETS | SYSTEM VIEW | MEMORY | 10 | Fixed | NULL | 384 | 0 | 16434816 | 0 | 0 | NULL | 2018-04-23 11:51:32 | NULL | NULL | utf8_general_ci | NULL | max_rows=43690 | | | def | information_schema | COLLATIONS | SYSTEM VIEW | MEMORY | 10 | Fixed | NULL | 231 | 0 | 16704765 | 0 | 0 | NULL | 2018-04-23 11:51:32 | NULL | NULL | utf8_general_ci | NULL | max_rows=72628 | | ... | def | zentao | zt_usertpl | BASE TABLE | MyISAM | 10 | Dynamic | 0 | 0 | 0 | 281474976710655 | 1024 | 0 | 1 | 2017-08-16 16:36:45 | 2017-08-16 16:36:45 | NULL | utf8_general_ci | NULL | | | +---------------+--------------------+------------------------------------------------------+-------------+--------------------+---------+------------+------------+----------------+-------------+--------------------+--------------+-----------+----------------+---------------------+---------------------+---------------------+-------------------+----------+--------------------+--------------------------------------------+ 525 rows in set (3.03 sec) mysql> SHOW TABLES FROM zentao; +-------------------+ | Tables_in_zentao | +-------------------+ | zt_action | | zt_block | | zt_branch | ... | zt_usertpl | +-------------------+ 48 rows in set (0.00 sec)
COLUMNS 表
存储表中的列信息，包括表有多少列、每个列的类型等。SHOW COLUMNS FROM schemaname.tablename 命令从这个表获取结果。
mysql> SELECT * FROM COLUMNS LIMIT 2,5; +---------------+--------------------+----------------+--------------------+------------------+----------------+-------------+-----------+--------------------------+------------------------+-------------------+---------------+--------------------+--------------------+-----------------+-------------+------------+-------+------------+----------------+-----------------------+ | TABLE_CATALOG | TABLE_SCHEMA | TABLE_NAME | COLUMN_NAME | ORDINAL_POSITION | COLUMN_DEFAULT | IS_NULLABLE | DATA_TYPE | CHARACTER_MAXIMUM_LENGTH | CHARACTER_OCTET_LENGTH | NUMERIC_PRECISION | NUMERIC_SCALE | DATETIME_PRECISION | CHARACTER_SET_NAME | COLLATION_NAME | COLUMN_TYPE | COLUMN_KEY | EXTRA | PRIVILEGES | COLUMN_COMMENT | GENERATION_EXPRESSION | +---------------+--------------------+----------------+--------------------+------------------+----------------+-------------+-----------+--------------------------+------------------------+-------------------+---------------+--------------------+--------------------+-----------------+-------------+------------+-------+------------+----------------+-----------------------+ | def | information_schema | CHARACTER_SETS | DESCRIPTION | 3 | | NO | varchar | 60 | 180 | NULL | NULL | NULL | utf8 | utf8_general_ci | varchar(60) | | | select | | | | def | information_schema | CHARACTER_SETS | MAXLEN | 4 | 0 | NO | bigint | NULL | NULL | 19 | 0 | NULL | NULL | NULL | bigint(3) | | | select | | | | def | information_schema | COLLATIONS | COLLATION_NAME | 1 | | NO | varchar | 32 | 96 | NULL | NULL | NULL | utf8 | utf8_general_ci | varchar(32) | | | select | | | | def | information_schema | COLLATIONS | CHARACTER_SET_NAME | 2 | | NO | varchar | 32 | 96 | NULL | NULL | NULL | utf8 | utf8_general_ci | varchar(32) | | | select | | | | def | information_schema | COLLATIONS | ID | 3 | 0 | NO | bigint | NULL | NULL | 19 | 0 | NULL | NULL | NULL | bigint(11) | | | select | | | +---------------+--------------------+----------------+--------------------+------------------+----------------+-------------+-----------+--------------------------+------------------------+-------------------+---------------+--------------------+--------------------+-----------------+-------------+------------+-------+------------+----------------+-----------------------+ 5 rows in set (0.08 sec)
STATISTICS 表
表索引的信息。SHOW INDEX FROM schemaname.tablename; 命令从这个表获取结果。
mysql> SHOW INDEX FROM szhuizhong.users; +-------+------------+---------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+ | Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment | +-------+------------+---------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+ | users | 0 | PRIMARY | 1 | UserID | A | 1460 | NULL | NULL | | BTREE | | | | users | 0 | Account_index | 1 | Account | A | 1460 | NULL | NULL | | BTREE | | | | users | 1 | CorpID | 1 | FromID | A | 2 | NULL | NULL | YES | BTREE | | | +-------+------------+---------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+ 3 rows in set (0.00 sec)
USER_PRIVILEGES 表
用户权限表。内容源自 mysql.user 授权表。是非标准表。
mysql> SELECT * FROM USER_PRIVILEGES; +-------------------------+---------------+-------------------------+--------------+ | GRANTEE | TABLE_CATALOG | PRIVILEGE_TYPE | IS_GRANTABLE | +-------------------------+---------------+-------------------------+--------------+ | 'mysql.sys'@'localhost' | def | USAGE | NO | | 'root'@'%' | def | SELECT | YES | | 'root'@'%' | def | INSERT | YES | | 'root'@'%' | def | UPDATE | YES | | 'root'@'%' | def | DELETE | YES | | 'root'@'%' | def | CREATE | YES | | 'root'@'%' | def | DROP | YES | | 'root'@'%' | def | RELOAD | YES | | 'root'@'%' | def | SHUTDOWN | YES | | 'root'@'%' | def | PROCESS | YES | | 'root'@'%' | def | FILE | YES | | 'root'@'%' | def | REFERENCES | YES | | 'root'@'%' | def | INDEX | YES | | 'root'@'%' | def | ALTER | YES | | 'root'@'%' | def | SHOW DATABASES | YES | | 'root'@'%' | def | SUPER | YES | | 'root'@'%' | def | CREATE TEMPORARY TABLES | YES | | 'root'@'%' | def | LOCK TABLES | YES | | 'root'@'%' | def | EXECUTE | YES | | 'root'@'%' | def | REPLICATION SLAVE | YES | | 'root'@'%' | def | REPLICATION CLIENT | YES | | 'root'@'%' | def | CREATE VIEW | YES | | 'root'@'%' | def | SHOW VIEW | YES | | 'root'@'%' | def | CREATE ROUTINE | YES | | 'root'@'%' | def | ALTER ROUTINE | YES | | 'root'@'%' | def | CREATE USER | YES | | 'root'@'%' | def | EVENT | YES | | 'root'@'%' | def | TRIGGER | YES | | 'root'@'%' | def | CREATE TABLESPACE | YES | +-------------------------+---------------+-------------------------+--------------+ 29 rows in set (0.00 sec)
SCHEMA_PRIVILEGES 表
方案权限表。给出了关于方案（数据库）权限的信息。内容来自 mysql.db 授权表。是非标准表。
mysql> SELECT * FROM SCHEMA_PRIVILEGES; +-------------------------+---------------+--------------+-------------------------+--------------+ | GRANTEE | TABLE_CATALOG | TABLE_SCHEMA | PRIVILEGE_TYPE | IS_GRANTABLE | +-------------------------+---------------+--------------+-------------------------+--------------+ | 'mysql.sys'@'localhost' | def | sys | TRIGGER | NO | | 'root'@'%' | def | mysql | SELECT | YES | | 'root'@'%' | def | mysql | INSERT | YES | | 'root'@'%' | def | mysql | UPDATE | YES | | 'root'@'%' | def | mysql | DELETE | YES | | 'root'@'%' | def | mysql | CREATE | YES | | 'root'@'%' | def | mysql | DROP | YES | | 'root'@'%' | def | mysql | REFERENCES | YES | | 'root'@'%' | def | mysql | INDEX | YES | | 'root'@'%' | def | mysql | ALTER | YES | | 'root'@'%' | def | mysql | CREATE TEMPORARY TABLES | YES | | 'root'@'%' | def | mysql | LOCK TABLES | YES | | 'root'@'%' | def | mysql | EXECUTE | YES | | 'root'@'%' | def | mysql | CREATE VIEW | YES | | 'root'@'%' | def | mysql | SHOW VIEW | YES | | 'root'@'%' | def | mysql | CREATE ROUTINE | YES | | 'root'@'%' | def | mysql | ALTER ROUTINE | YES | | 'root'@'%' | def | mysql | EVENT | YES | | 'root'@'%' | def | mysql | TRIGGER | YES | +-------------------------+---------------+--------------+-------------------------+--------------+ 19 rows in set (0.00 sec)
TABLE_PRIVILEGES 表
表权限表。给出了关于表权限的信息。内容源自 mysql.tables_priv 授权表。是非标准表。
mysql> SELECT * FROM TABLE_PRIVILEGES; +-------------------------+---------------+--------------+------------+----------------+--------------+ | GRANTEE | TABLE_CATALOG | TABLE_SCHEMA | TABLE_NAME | PRIVILEGE_TYPE | IS_GRANTABLE | +-------------------------+---------------+--------------+------------+----------------+--------------+ | 'mysql.sys'@'localhost' | def | sys | sys_config | SELECT | NO | +-------------------------+---------------+--------------+------------+----------------+--------------+ 1 row in set (0.00 sec)
COLUMN_PRIVILEGES 表
列权限表。给出了关于列权限的信息。内容源自 mysql.columns_priv 授权表。是非标准表。
mysql> SELECT * FROM COLUMN_PRIVILEGES; Empty set (0.00 sec)
COLLATIONS 表
提供了关于各字符集的对照信息。SHOW COLLATION; 命令从这个表获取结果。
mysql> SELECT * FROM COLLATIONS; +--------------------------+--------------------+-----+------------+-------------+---------+ | COLLATION_NAME | CHARACTER_SET_NAME | ID | IS_DEFAULT | IS_COMPILED | SORTLEN | +--------------------------+--------------------+-----+------------+-------------+---------+ | big5_chinese_ci | big5 | 1 | Yes | Yes | 1 | | big5_bin | big5 | 84 | | Yes | 1 | | dec8_swedish_ci | dec8 | 3 | Yes | Yes | 1 | | dec8_bin | dec8 | 69 | | Yes | 1 | ... | gb18030_bin | gb18030 | 249 | | Yes | 1 | | gb18030_unicode_520_ci | gb18030 | 250 | | Yes | 8 | +--------------------------+--------------------+-----+------------+-------------+---------+ 222 rows in set (0.03 sec)
COLLATION_CHARACTER_SET_APPLICABILITY 表
指明了可用于校对的字符集。相当于 SHOW COLLATION 命令结果的前两个字段。
mysql> SELECT * FROM COLLATION_CHARACTER_SET_APPLICABILITY; +--------------------------+--------------------+ | COLLATION_NAME | CHARACTER_SET_NAME | +--------------------------+--------------------+ | big5_chinese_ci | big5 | | big5_bin | big5 | | dec8_swedish_ci | dec8 | ... | gb18030_bin | gb18030 | | gb18030_unicode_520_ci | gb18030 | +--------------------------+--------------------+ 222 rows in set (0.00 sec)
TABLE_CONSTRAINTS 表
描述了存在约束的表。以及表的约束类型。
mysql> SELECT * FROM TABLE_CONSTRAINTS; +--------------------+-------------------+--------------------+--------------+---------------------------+-----------------+ | CONSTRAINT_CATALOG | CONSTRAINT_SCHEMA | CONSTRAINT_NAME | TABLE_SCHEMA | TABLE_NAME | CONSTRAINT_TYPE | +--------------------+-------------------+--------------------+--------------+---------------------------+-----------------+ | def | mysql | PRIMARY | mysql | columns_priv | PRIMARY KEY | | def | mysql | PRIMARY | mysql | db | PRIMARY KEY | | def | mysql | PRIMARY | mysql | engine_cost | PRIMARY KEY | | def | mysql | PRIMARY | mysql | event | PRIMARY KEY | | def | mysql | PRIMARY | mysql | func | PRIMARY KEY | | def | mysql | PRIMARY | mysql | gtid_executed | PRIMARY KEY | | def | mysql | PRIMARY | mysql | help_category | PRIMARY KEY | | def | mysql | name | mysql | help_category | UNIQUE | | def | mysql | PRIMARY | mysql | help_keyword | PRIMARY KEY | | def | mysql | name | mysql | help_keyword | UNIQUE | | def | mysql | PRIMARY | mysql | help_relation | PRIMARY KEY | | def | mysql | PRIMARY | mysql | help_topic | PRIMARY KEY | | def | mysql | name | mysql | help_topic | UNIQUE | | def | mysql | PRIMARY | mysql | innodb_index_stats | PRIMARY KEY | | def | mysql | PRIMARY | mysql | innodb_table_stats | PRIMARY KEY | | def | mysql | PRIMARY | mysql | ndb_binlog_index | PRIMARY KEY | | def | mysql | PRIMARY | mysql | plugin | PRIMARY KEY | | def | mysql | PRIMARY | mysql | proc | PRIMARY KEY | | def | mysql | PRIMARY | mysql | procs_priv | PRIMARY KEY | | def | mysql | PRIMARY | mysql | proxies_priv | PRIMARY KEY | | def | mysql | PRIMARY | mysql | server_cost | PRIMARY KEY | | def | mysql | PRIMARY | mysql | servers | PRIMARY KEY | | def | mysql | PRIMARY | mysql | slave_master_info | PRIMARY KEY | | def | mysql | PRIMARY | mysql | slave_relay_log_info | PRIMARY KEY | | def | mysql | PRIMARY | mysql | slave_worker_info | PRIMARY KEY | | def | mysql | PRIMARY | mysql | tables_priv | PRIMARY KEY | | def | mysql | PRIMARY | mysql | time_zone | PRIMARY KEY | | def | mysql | PRIMARY | mysql | time_zone_leap_second | PRIMARY KEY | | def | mysql | PRIMARY | mysql | time_zone_name | PRIMARY KEY | | def | mysql | PRIMARY | mysql | time_zone_transition | PRIMARY KEY | | def | mysql | PRIMARY | mysql | time_zone_transition_type | PRIMARY KEY | | def | mysql | PRIMARY | mysql | user | PRIMARY KEY | | def | sys | PRIMARY | sys | sys_config | PRIMARY KEY | | def | zentao | PRIMARY | zentao | zt_action | PRIMARY KEY | ... | def | zentao | account | zentao | zt_usergroup | UNIQUE | | def | zentao | PRIMARY | zentao | zt_userquery | PRIMARY KEY | | def | zentao | PRIMARY | zentao | zt_usertpl | PRIMARY KEY | +--------------------+-------------------+--------------------+--------------+---------------------------+-----------------+ 213 rows in set (0.37 sec)
KEY_COLUMN_USAGE 表
描述了具有约束的键列。
mysql> SELECT * FROM KEY_COLUMN_USAGE; +--------------------+-------------------+--------------------+---------------+--------------+---------------------------+--------------------+------------------+-------------------------------+-------------------------+-----------------------+------------------------+ | CONSTRAINT_CATALOG | CONSTRAINT_SCHEMA | CONSTRAINT_NAME | TABLE_CATALOG | TABLE_SCHEMA | TABLE_NAME | COLUMN_NAME | ORDINAL_POSITION | POSITION_IN_UNIQUE_CONSTRAINT | REFERENCED_TABLE_SCHEMA | REFERENCED_TABLE_NAME | REFERENCED_COLUMN_NAME | +--------------------+-------------------+--------------------+---------------+--------------+---------------------------+--------------------+------------------+-------------------------------+-------------------------+-----------------------+------------------------+ | def | mysql | PRIMARY | def | mysql | columns_priv | Host | 1 | NULL | NULL | NULL | NULL | | def | mysql | PRIMARY | def | mysql | columns_priv | Db | 2 | NULL | NULL | NULL | NULL | | def | mysql | PRIMARY | def | mysql | columns_priv | User | 3 | NULL | NULL | NULL | NULL | | def | mysql | PRIMARY | def | mysql | columns_priv | Table_name | 4 | NULL | NULL | NULL | NULL | | def | mysql | PRIMARY | def | mysql | columns_priv | Column_name | 5 | NULL | NULL | NULL | NULL | ... | def | mysql | PRIMARY | def | mysql | time_zone_leap_second | Transition_time | 1 | NULL | NULL | NULL | NULL | | def | mysql | PRIMARY | def | mysql | time_zone_name | Name | 1 | NULL | NULL | NULL | NULL | | def | mysql | PRIMARY | def | mysql | time_zone_transition | Time_zone_id | 1 | NULL | NULL | NULL | NULL | | def | mysql | PRIMARY | def | mysql | time_zone_transition | Transition_time | 2 | NULL | NULL | NULL | NULL | | def | mysql | PRIMARY | def | mysql | time_zone_transition_type | Time_zone_id | 1 | NULL | NULL | NULL | NULL | | def | mysql | PRIMARY | def | mysql | time_zone_transition_type | Transition_type_id | 2 | NULL | NULL | NULL | NULL | | def | mysql | PRIMARY | def | mysql | user | Host | 1 | NULL | NULL | NULL | NULL | | def | mysql | PRIMARY | def | mysql | user | User | 2 | NULL | NULL | NULL | NULL | | def | sys | PRIMARY | def | sys | sys_config | variable | 1 | NULL | NULL | NULL | NULL | +--------------------+-------------------+--------------------+---------------+--------------+---------------------------+--------------------+------------------+-------------------------------+-------------------------+-----------------------+------------------------+ 278 rows in set (0.03 sec)
ROUTINES 表
提供了关于存储子程序（存储程序和函数）的信息。此时，ROUTINES 表不包含自定义函数（UDF）。名为“mysql.proc name”的列指明了对应于 INFORMATION_SCHEMA.ROUTINES 表的 mysql.proc 列。
VIEWS 表
给出了关于数据库中的视图的信息。需要有 show views 权限，否则无法查看视图信息。
mysql> SELECT * FROM VIEWS LIMIT 1\G
*************************** 1. row ***************************
TABLE_CATALOG: def
TABLE_SCHEMA: sys
TABLE_NAME: host_summary
VIEW_DEFINITION: select if(isnull(`performance_schema`.`accounts`.`HOST`),'background',`performance_schema`.`accounts`.`HOST`) AS `host`,sum(`stmt`.`total`) AS `statements`,`sys`.`format_time`(sum(`stmt`.`total_latency`)) AS `statement_latency`,`sys`.`format_time`(ifnull((sum(`stmt`.`total_latency`) / nullif(sum(`stmt`.`total`),0)),0)) AS `statement_avg_latency`,sum(`stmt`.`full_scans`) AS `table_scans`,sum(`io`.`ios`) AS `file_ios`,`sys`.`format_time`(sum(`io`.`io_latency`)) AS `file_io_latency`,sum(`performance_schema`.`accounts`.`CURRENT_CONNECTIONS`) AS `current_connections`,sum(`performance_schema`.`accounts`.`TOTAL_CONNECTIONS`) AS `total_connections`,count(distinct `performance_schema`.`accounts`.`USER`) AS `unique_users`,`sys`.`format_bytes`(sum(`mem`.`current_allocated`)) AS `current_memory`,`sys`.`format_bytes`(sum(`mem`.`total_allocated`)) AS `total_memory_allocated` from (((`performance_schema`.`accounts` join `sys`.`x$host_summary_by_statement_latency` `stmt` on((`performance_schema`.`accounts`.`HOST` = `stmt`.`host`))) join `sys`.`x$host_summary_by_file_io` `io` on((`performance_schema`.`accounts`.`HOST` = `io`.`host`))) join `sys`.`x$memory_by_host_by_current_bytes` `mem` on((`performance_schema`.`accounts`.`HOST` = `mem`.`host`))) group by if(isnull(`performance_schema`.`accounts`.`HOST`),'background',`performance_schema`.`accounts`.`HOST`)
CHECK_OPTION: NONE
IS_UPDATABLE: NO
DEFINER: mysql.sys@localhost
SECURITY_TYPE: INVOKER
CHARACTER_SET_CLIENT: utf8
COLLATION_CONNECTION: utf8_general_ci
1 row in set (0.03 sec)
TRIGGERS 表
提供了关于触发程序的信息。必须有 super 权限才能查看该表。
mysql> SELECT * FROM TRIGGERS LIMIT 1\G
*************************** 1. row ***************************
TRIGGER_CATALOG: def
TRIGGER_SCHEMA: sys
TRIGGER_NAME: sys_config_insert_set_user
EVENT_MANIPULATION: INSERT
EVENT_OBJECT_CATALOG: def
EVENT_OBJECT_SCHEMA: sys
EVENT_OBJECT_TABLE: sys_config
ACTION_ORDER: 1
ACTION_CONDITION: NULL
ACTION_STATEMENT: BEGIN IF @sys.ignore_sys_config_triggers != true AND NEW.set_by IS NULL THEN SET NEW.set_by = USER(); END IF; END
ACTION_ORIENTATION: ROW
ACTION_TIMING: BEFORE
ACTION_REFERENCE_OLD_TABLE: NULL
ACTION_REFERENCE_NEW_TABLE: NULL
ACTION_REFERENCE_OLD_ROW: OLD
ACTION_REFERENCE_NEW_ROW: NEW
CREATED: 2017-05-27 11:18:43.60
SQL_MODE:
DEFINER: mysql.sys@localhost
CHARACTER_SET_CLIENT: utf8
COLLATION_CONNECTION: utf8_general_ci
DATABASE_COLLATION: utf8_general_ci
1 row in set (0.00 sec)
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本文标题：MySQL之information_schema数据库详细讲解
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