How does Oracle manage to query a view?

Question

Hello,
We are using an Oracle 9i database.
We are using Discoverer, but I experience some difficulties understanding a query built by Discoverer.
I think this is a basic explanation that I want. That's the reason why I decided to post my message under this forum.
The query I would like an explanation is such as this :
SELECT C.colB, count(C.col1), count(C.col2)
FROM (select b.colA, b.colB, a.col1, MAX(a.col2)
FROM tableA, tableB
WHERE a.joinB = b.joinA
GROUP BY b.colA, b.colB, a.col1) C
WHERE C.colA = 'blabla'
GROUP BY C.colB;
So, my question is :
Is the sub-select, (maybe it's not the right name!), executed regardless the condition "C.colA = 'blabla'", basically does it build the full view regardless the "external" condition ?
or, is the sub-select aware of the condition when it is built into memory ?
Is there a web-site, or documentation about such question?
In advance, thanks a lot for your help.
Olivier

Answer 1

Check if the following helps. In your case subquery will be executed first because of 'MAX'.
http://download-west.oracle.com/docs/cd/B10501_01/server.920/a96533/opt_ops.htm#1005152
/*****Extract from above link**********/
Mergeable and Nonmergeable Views
The optimizer can merge a view into a referencing query block when the view has one or more base tables, provided the view does not contain any of the following:
Set operators (UNION, UNION ALL, INTERSECT, MINUS)
A CONNECT BY clause
A ROWNUM pseudocolumn
Aggregate functions (AVG, COUNT, MAX, MIN, SUM) in the select list
When a view contains one of the following structures, it can be merged into a referencing query block only if Complex View Merging is enabled:
A GROUP BY clause
A DISTINCT operator in the select list
/*********************************************/