show databases;

select table_name from information_schema.tables where table_schema='database_name' and table_type='base table';

select column_name from information_schema.columns where table_schema='database_name' and table_name='table_name';

select column_name,data_type from information_schema.columns where table_schema='database_name' and table_name='table_name';

select * from sysdatabases;

select * from sysobjects where xtype='U';
xtype='U':表示所有用户表，xtype='S':表示所有系统表。

select name from syscolumns where id=Object_Id('table_name');

select sc.name,st.name from syscolumns sc,systypes st where sc.xtype=st.xtype and sc.id in(select id from sysobjects where xtype='U' and name='table_name');

select * from v$tablespace;--查询表空间(需要一定权限)

select * from user_tables;

select column_name from user_tab_columns where table_name = 'table_name';--表名要全大写

select column_name, data_type from user_tab_columns where table_name = 'table_name';-