Select from refcursor in PL/SQL pkg

Question

Greetings,
I would like to be able to return a set of values in some sort of temporary structure(temp table, cursor..it don't matter) to be used as part of the WHERE clause in several other queries. Normally I would just use a query in each of the other queries like so:
SELECT a.1, a.2, a.3
FROM bigtbl a,
(SELECT x, y, z FROM criteriakeys)b
WHERE a.x = b.x AND
a.y = b.y AND
a.z = b.z
SELECT c.1, c.2, c.3
FROM bigrtbl c,
(SELECT x, y, z FROM criteriakeys)b
WHERE c.x = b.x AND
c.y = b.y AND
c.z = b.z
etc...
The problem is that the query(b in the above) is a complex one that will be hitting against a very large number of records. I understand that temp tables are not supposed to be needed in Oracle. I haven't in 10 years and until now did not even know that it was possible. So I would use a refcursor BUT I don't know how to use a refcursor as the base of a SELECT something like:
rc ref cursor;
getcriteriakeys(rc); -- send in a refcursor and come back full of records
SELECT a.1, a.2, a.3
FROM bigtbl a,
(SELECT x, y, z FROM rc)b
WHERE a.x = b.x AND
a.y = b.y AND
a.z = b.z
This seems, to me anyway, to be an obvious use of refcursor but I cannot find any mention of it either way. I can infer from the way refcursors are used that they only send back a row at a time. This is nice but would produce sub-optimal results.
Any suggestions or comments will be welcome.
Thanks

Answer 1

If query b is really complex, takes a "while" to execute (long enough that you don't want to do it more than once in a set of statements), and not straightforward as in your example, one option would be to load the results of query b into a global temporary table - and then join to that table in your successive query.
A ref cursor is not really applicable in this context.
The routine would be something like:
insert into gtt
  select * from ...; -- complex query b
-- the selects below would either be cursor for loops or single row select/into
-- (couldn't tell from your sample)
select *
  from a, gtt
where a.x = gtt.x
   and ...;
select *
  from b, gtt
where b.x = gtt.x
   and ...;