转自：http://www.cnblogs.com/qingsong-do/archive/2011/11/29/2267244.html

获取表：

select table_name from user_tables; //当前用户的表      select table_name from all_tables; //所有用户的表  select table_name from dba_tables; //包括系统表select table_name from dba_tables where owner='用户名'user_tables：table_name,tablespace_name,last_analyzed等dba_tables：ower,table_name,tablespace_name,last_analyzed等all_tables：ower,table_name,tablespace_name,last_analyzed等all_objects：ower,object_name,subobject_name,object_id,created,last_ddl_time,timestamp,status等

获取表字段：

select * from user_tab_columns where Table_Name='用户表';select * from all_tab_columns where Table_Name='用户表';select * from dba_tab_columns where Table_Name='用户表';user_tab_columns：table_name,column_name,data_type,data_length,data_precision,data_scale,nullable,column_id等all_tab_columns ：ower,table_name,column_name,data_type,data_length,data_precision,data_scale,nullable,column_id等dba_tab_columns：ower,table_name,column_name,data_type,data_length,data_precision,data_scale,nullable,column_id等

获取表注释：

select * from user_tab_commentsuser_tab_comments：table_name,table_type,comments--相应的还有dba_tab_comments，all_tab_comments，这两个比user_tab_comments多了ower列。

获取字段注释：

select * from user_col_commentsuser_col_comments：table_name,column_name,comments