获取表字段：
select *
from user_tab_columns
where Table_Name='用户表'
order by column_name
获取表注释：
select * from user_tab_columns where Table_Name='用户表' order by column_name
获取表的列注释
select * from user_COL_comments where table_name='用户表'
获取表的列信息
select *
from user_tab_cols
where table_name=upper('用户表')
