Re: SQL Question

Because compared to the other joins, it is slow. Can force full table scans.
I think the only slower one is not exists

M

Paul Wiles wrote in message <374bca70_at_newsread3.dircon.co.uk>...
>Why do you refer to 'not in' as dreaded ?
>
>
>Mark Gumbs wrote in message <374bc56e.0_at_145.227.194.253>...
>>The two statements in your instance are equivalent but bear in mind that
>>when using the minus, the statemennt has to be in the correct order, ie
>>tableA minus Tableb is not the same as tableB minus tableA.
>>
>>Use set operators instead of the dreaded not in if you can, it should be
>>faster.
>>
>>Mark
>>
>>Paul Davies wrote in message <374bb823_at_newsread3.dircon.co.uk>...
>>>Are intersects and joins equivalent?
>>>
>>>So is the query:
>>>
>>>select part from orders_list1
>>>intersect
>>>select part from orders_list2
>>>
>>>the same as
>>>
>>>select a.part from orders_list1 a, orders_list2 b where b.part = a.part
>>>
>>>Similarly is
>>>
>>>select part from orders_list1
>>>minus
>>>select part_from orders_list2
>>>
>>>the same as
>>>
>>>select part from orders_list1 where part not in (select part from
>>>orders_list2)
>>>
>>>If they are equivalent, when should one choose to use a set operator as
>>>opposed to a join or not in query?
>>>
>>>Help appreciated
>>>
>>>Paul
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>
>>
>
>
Received on Wed May 26 1999 - 05:43:21 CDT