> However, this query does not give me the result I expected. It appears that
> the database engine first calculates the cartesian product of the tables A
> and B and then evaluates the query. Hence, I get multiple matches for
Yup.. WHERE filters the results of the join.
> Is there any way to do this, other than using UNION??
This is what you want. I think you could come out with what you want in
other ways, but this is by far the most appropriate.
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TIP 9: the planner will ignore your desire to choose an index scan if your
joining column's datatypes do not match
