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  2. MIDRANGE-L
  3. February 2009

RE: SQL index possible with keys from two tables?

So if I've got this right, the order/invoice table has the order id, a
salesrep id, and the customer id (among other stuff). The customer table
has the customer id and the territory id. The fast SQL is something
along the lines of:

SELECT * FROM orders WHERE salesrep = 12345

And the "slow" sql is along the lines of:

SELECT orders.* FROM orders
JOIN customer
ON order.customerid = customer.customerid
AND customer.territory = 'EAST'


Do you have an index on customer & territory? I'd love to see the visual
explain of this query. An index on customer by id and territory should
be a covering index preventing the trip to the customer physical (unless
you're getting customer info too)

-Walden


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