"A. Brandic" wrote:
>
> Sorry Jules!
>
> You were right, it is displaying 'MN' number of rows. I did not think it
> would have but it does. I've just created a small table with 5 records
> in it and used it in the above query instead of Streams table and it
> displaye over 60000 recods instead of 15000. My view was that the extra
> table (rows from the extra table) would have been ignored after the
> execution of the query.
Well, I regret to say it... but in that case, you don't understand SQL
syntax.
Suppose A, B are joined by a unique field ID in each of them.
SELECT * FROM A,B;
Will return a cartesian product - one row for each possible pairing of
rows, one from A and one from B.
SELECT * FROM A,B WHERE A.ID = B.ID;
Will only return those pairings where the two columns in the cartesian
product 'A.ID' and 'B.ID' have identical values. This is, in general, a
much more useful query :-)
If you think about it for a while, you'll see why this is the only sane
way to interpret the queries.
Jules
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