这个表(视图)是在MySQL5以后的才有的,现在MySQL4应该是很少了,所以都围绕着MySQL5来讲解，information_schema是用于存储数据库元数据的表，它保存了数据库名，表名，列名等信息，让我们从爆破表名到了可以直接查询。
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)
我们经常用到的几个表
-
SCHEMATA表 ： 提供了当前mysql实例中所有数据库的信息。
-
TABLES 表 ： 提供了关于数据库中的表的信息。
-
COLUMNS 表 ：提供了表中的列信息
SCHEMATA:
mysql> select * from information_schema.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 | mysqltest | latin1 | latin1_swedish_ci | NULL |
| def | performance_schema | utf8 | utf8_general_ci | NULL |
+--------------+--------------------+----------------------------+------------------------+----------+
4 rows in set (0.00 sec)
TABLES:
mysql> select table_name from information_schema.tables where table_schema=0x6D7973716C74657374; //注意这里不用引号就要把数据库名转为16进制
+------------+
| table_name |
+------------+
| admin |
+------------+
1 row in set (0.00 sec)
COLUMNS：
mysql> select column_name from information_schema.columns where table_name=0x61646D696E;
+-------------+
| column_name |
+-------------+
| id |
| username |
| password |
+-------------+
3 rows in set (0.00 sec)
我们前面说过information_schema储存的是所有数据库的信息,假如我的数据库 mysqltest1 mysqltest2 都存在admin表的话 它都会显示出来
mysql> select column_name from information_schema.columns where table_name=0x61646D696E;
+-------------+
| column_name |
+-------------+
| id |
| username |
| password |
| id |
| user |
| pass |
+-------------+
6 rows in set (0.00 sec)
所以要指定数据库
mysql> select column_name from information_schema.columns where table_name=0x61646D696E and table_schema=0x6D7973716C74657374;
+-------------+
| column_name |
+-------------+
| id |
| username |
| password |
+-------------+
3 rows in set (0.00 sec)
user 表保存的用户密码 和host等等信息
mysql> select user,password from user;
+------------------+-------------------------------------------+
| user | password |
+------------------+-------------------------------------------+
| root | *81F5E21E35407D884A6CD4A731AEBFB6AF209E1B |
| root | *81F5E21E35407D884A6CD4A731AEBFB6AF209E1B |
| root | *81F5E21E35407D884A6CD4A731AEBFB6AF209E1B |
| root | *81F5E21E35407D884A6CD4A731AEBFB6AF209E1B |
| debian-sys-maint | *764E40048679D21BBB07CB8DDD18465359DAB4CA |
+------------------+-------------------------------------------+
5 rows in set (0.00 sec)
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