PLSQL导出Oracle表结构

SELECT t1.Table_Name AS "表名称",  
t3.comments AS "表说明",   
t1.Column_Name AS "字段名称",  
t1.Data_Type AS "数据类型",  
t1.Data_Length AS "长度",  
t1.NullAble AS "是否为空",  
t2.Comments AS "字段说明",  
t1.Data_Default "默认值" 
FROM cols t1 left join user_col_comments t2  
on t1.Table_name=t2.Table_name and t1.Column_Name=t2.Column_Name  
left join user_tab_comments t3   
on t1.Table_name=t3.Table_name   
WHERE NOT EXISTS ( SELECT t4.Object_Name FROM User_objects t4  
WHERE t4.Object_Type='TABLE'  
AND t4.Temporary='Y'  
AND t4.Object_Name=t1.Table_Name )  

ORDER BY t1.Table_Name, t1.Column_ID;