[mysql] information_schema 数据库
information_schema 数据库中存储了许多动态的信息.
其中有一张表叫 COLUMNS.
执行 select * from information_schema.COLUMNS; 将输出很多行
它记录了所有数据库中的列的名称等属性
mysql> select * from COLUMNS;
...
1883 rows in set
--------------------------------------------
举个例子:
mysql> use information_schema;
Database changed
mysql> select * from COLUMNS where table_name='ships';
+---------------+-----------------+------------+-------------+------------------+----------------+-------------+-----------+--------------------------+------------------------+-------------------+---------------+--------------------+--------------------+----------------+-------------+------------+-------+---------------------------------+----------------+
| 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 |
+---------------+-----------------+------------+-------------+------------------+----------------+-------------+-----------+--------------------------+------------------------+-------------------+---------------+--------------------+--------------------+----------------+-------------+------------+-------+---------------------------------+----------------+
| def | test_shipsinww2 | ships | name | 1 | NULL | YES | varchar | 20 | 40 | NULL | NULL | NULL | gbk | gbk_chinese_ci | varchar(20) | | | select,insert,update,references | |
| def | test_shipsinww2 | ships | class | 2 | NULL | YES | varchar | 20 | 40 | NULL | NULL | NULL | gbk | gbk_chinese_ci | varchar(20) | | | select,insert,update,references | |
| def | test_shipsinww2 | ships | launched | 3 | NULL | YES | year | NULL | NULL | NULL | NULL | NULL | NULL | NULL | year(4) | | | select,insert,update,references | |
+---------------+-----------------+------------+-------------+------------------+----------------+-------------+-----------+--------------------------+------------------------+-------------------+---------------+--------------------+--------------------+----------------+-------------+------------+-------+---------------------------------+----------------+
3 rows in set (0.04 sec)