June 7, 2005 at 8:15 am
Standard or Enterprise?
June 7, 2005 at 8:19 am
Wtf Dev????????
Gonna have to have a little talk with my boss!!!!!!
June 7, 2005 at 8:20 am
FYI - I just tested (and verified) that this behavior exists in Enterprise SP3a as well as Personal Edition SP3a.
June 7, 2005 at 8:23 am
Possible answer off the MS TechNet site - The answer makes sense!
(in response to the exact same question posed here):
The way the first query is written forces the joins in a specific order.
This can be functionally useful if you have a combination of inner and outer
join, and it works more or less the same as using derived tables or
subqueries.
However forcing the join order in that way prevents the Query Optimizer from
considering certain query plans, and in this case prevents it from
considering a better query plan. (In some rare cases forcing the join order
can also be used the other way around, to prevent the Query Optimizer from
considering some less-than-optimal query plans). Writing the query like you
do in query 2, allows the Query Optimizer to consider more possible query
plans, one of which turns out to be better than the one used by query 1 and
3.
--
Jacco Schalkwijk
SQL Server MVP
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