SQL & PL/SQL

Hi,
I'm a new Oracle PL/SQL developer and at the moment I'm making a migration from Visual Fox Pro to Oracle.
I've a Fox Pro script that takes results from several tables and then execute a select statement at those results.
Example:
SELECT *
FROM table1
UNION
SELECT *
FROM table2
UNION
SELECT *
FROM table3
INTO CURSOR (data_cursor);

SELECT SUM(column1), SUM(column2)
FROM data_cursor
WHERE column3 = XXX;

I need to implement this in PL/SQL and after making some research i found out that using the TABLE function for storing the results could be a possible solution.
I also need to update and delete data from "data_cursor".
Is this right or a better solution is possible??? Is it possible to make a view for each result and then query that view??

Thanks a lot,
Camilo

P.S.: Excuse me for my English....... i'm from Argentina.