Marc,
> select a.col1, b.col2 from a,b
> where a.col1 = b.col2
> or b.col2 is null
The above would select each record in a that matched a record in b, plus
each record in b for every possible a where b.col2 was null - not where
there was no match.
> select a.col1, b.col2 from a,b
> where a.col1 = b.col2
> or a.col1 not in (select b.col2 from b)
This would work, but it would be *much* slower than a UNION query. "Not
In" queries are perhaps the slowest you can run; see the earlier thread
"Query Problem" for a discussion. UNION queries are, in fact, very fast
... just awkward to code and manipulate.
-Josh
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