How to Select data using same column name from 3 remote database

Question

Hi,
Can anyone help me on how to get data with same column names from 3 remote database and a single alias.
Ex.
SELECT *
a.name, b.status, SUM(b.qty) qantity, MAX(b.date) date_as_of
FROM
*((table1@remotedatabase1, table1@remotedatabase2, table1@remotedatabase3)a,*
*(table1@remotedatabase1, table1@remotedatabase2, table1@remotedatabase3)b)*
WHERE b.dept = 'finance'
AND a.position = 'admin'
AND a.latest = 'Y' AND (b.status <> 'TRM') AND b.qty > 0;
GROUP BY a.name, b.status ;
NOTE: the bold statements is just an example of what I want to do but I always gets an error beacause of ambiguous columns.
Thanks in advnce. :)
Edited by: user12994685 on Jan 4, 2011 9:42 PM

Answer 1

user12994685 wrote:
Can anyone help me on how to get data with same column names from 3 remote database and a single alias.Invalid. This does not make sense and breaks all scope resolution rules. And whether this is in a single database, or uses tables across databases, is irrelevant.
Each object must be uniquely identified. So you cannot do this:
select * from (table1@remotedatabase1, table1@remotedatabase2, table1@remotedatabase3) a3 objects cannot share the same alias. Example:
SQL> select * from (dual, dual) d;
select * from (dual, dual) d
ERROR at line 1:
ORA-00907: missing right parenthesisYou need to combine the objects - using a join or union or similar. So it will need to be done as follows:
SQL> select * from (select * from dual d1, dual d2) d;
select * from (select * from dual d1, dual d2) d
ERROR at line 1:
ORA-00918: column ambiguously definedHowever, we need to have unique column names in a SQL projection - so the join of the tables need to project a unique set of columns. Thus:
SQL> select * from (select d1.dummy as dummy1, d2.dummy as dummy2 from dual d1, dual d2) d;
DUM DUM
X   X
SQL> I suggest that you look closely at what scope is and how it applies in the SQL language - and ignore whether the objects referenced are local or remote as it has no impact to fundamentals of scope resolution.