how about a link into otn.oracle.com, the documentation?
but in any case it is non-mergable, but that does NOT mean "not subject to predicate pushing"!
it is non mergable since the union operation implies a sort/distinct step. So, we cannot take that view (call it V) and just "merge it into a larger query", since we have to sort/distinct it before say joining it to something else.
We can (and will) push a predicate, so that:
select * from V where deptno = 50;
will be what you want - however,
select * from V where v.deptno = 50 and <whatever other join>
will not be merged into a single "query" -- the view must be preserved -- so we can sort/distinct it AND THEN join.
so, predicate pushing (different from merging) will be done...
</code>
http://asktom.oracle.com/pls/asktom/f?p=100:11:::::P11_QUESTION_ID:3561623983484#29347346730613 <code>
2) you would have to "not bind" that column - meaning you would be using dynamic sql - probably "method 3"
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