It is as follows:
As you can see in the attached screen shot, what QB does is to build a list of fields to which SQL operators are associated in a grid.
The general rule seems to be that adding fields vertically yields AND statments, whereas adding conditions horizontally yields OR statements.
The problem is that each column of Criteria yields a single parenthisized clause containing conditions connected by AND's. And those parenthesized clauses (each representing a criteria column) are then connected by ORs.
This is completely wrong and unusable!
There HAS to be a way of adding ORs inside of an AND clause.
To simplify the matter somewhat ...
You will see from my screenshot that what I was trying to acheive was something like:
(Field 1 - Condition) AND
(Field 2 - Condition) AND
(Field 3 - (Condition-A OR Condition-

)
That is not what the SQL generator produced. It produced something like:
(
(Field 1 - Condition) AND
(Field 2 - Condition) AND
(Field 3 - Condition-A)
)
OR
(Field 3 - Condition-
This is completely unusable. (And is the reverse of what one is normally trying to do).
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Either there is some way that I could'nt figure out, for the user to control parenthesis -- or this is not working in a sensible way.
There has got to be a simple way to test multiple conditions against a single field in a single clause.