Is there any difference between this:

SELECT a.Something FROM table1 a
LEFT JOIN table2 b ON a.ID_Account = b.ID_Account AND a.ID_Contract =
b.ID_Contract
WHERE a.ID_Contract = b.ID_Contract

and

SELECT a.Something FROM table1 a
LEFT JOIN table2 b ON a.ID_Account = b.ID_Account
WHERE a.ID_Contract = b.ID_Contract

?

Thank you in advance.

I think the where clause in the first query is not needed.
Have you compared the two execution plans?


ML

---
http://milambda.blogspot.com/

I think it is needed.

As much as I can see, results for both quesries are the same.

In your first query one condition is both in the join and in the where
clause. Try removing it from the where clause, that might affect the
execution plan.

Of course you should free the cache between individual tests.


ML

---
http://milambda.blogspot.com/

Petar,
the queries are identical:
because of the condition WHERE a.ID_Contract = b.ID_Contract (which
means that b.ID_Contract is not null), your left OUTER join essentially
becomes an INNER one. In most cases the optimizer recognizes that no
problem. Try removing LEFT keyword altogether and see if it affects the
execution plan, most probably it will not.

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