oracle中已知个数据库名 如何查出里面所有表名及表结构

select a.owner 所属用户,a.table_name 表名,a.column_name 字段名,a.data_type 字段类型,a.字段长度,a.字段精度,a.是否为空,a.创建日期,a.最后修改日期,
case when a.owner=d.owner and a.table_name=d.table_name and a.column_name=d.column_name then '主键' else '' end 是否主键
from
(select a.owner,a.table_name,b.column_name,b.data_type,case when b.data_precision is null then b.data_length else data_precision end 字段长度,
data_scale 字段精度,
decode(nullable,'Y','√','N','×') 是否为空,c.created 创建日期,c.last_ddl_time 最后修改日期
from all_tables a,all_tab_columns b,all_objects c
where a.table_name=b.table_name and a.owner=b.owner
and a.owner=c.owner
and a.table_name=c.object_name
and a.owner='SCOTT'--此处用户名可以更改，但必须大写英文，也可以把这行删除
and c.object_type='TABLE') a
left join
(select a.owner,a.table_name,a.column_name,a.constraint_name from user_cons_columns a, user_constraints b
where a.constraint_name = b.constraint_name and b.constraint_type = 'P') d
on a.owner=d.owner and a.table_name=d.table_name and a.column_name=d.column_name
order by a.owner,a.table_name;

select * from dba_tables（用sys登陆)

给你一个连接，你自己可以看一下，很有帮助的http://www.2cto.com/database/201304/204803.html