HI,
the answer to ur querry lies with the fact that 'minus' takes less sort's in
memory. try finding it out with the autotrace command.
and also due to less sorts in memory it has less no of rows processed for
the same result then 'not in'
one more thing is for any querry it sends less amount of data to client via
sql*net
i feel ur question is answered.
saurabh
----- Original Message -----
To: Multiple recipients of list ORACLE-L <[EMAIL PROTECTED]>
Sent: Friday, February 09, 2001 2:33 AM
> Hello all.
>
> I read a question concerning the use of the MINUS function earlier and I
had
> not heard of it before today. After some experimenting with it, I was
quite
> amazed at the speed of this function compared to using NOT IN.
>
> Considering the following:
>
> Query One
>
> select distinct icons from inpatient
> minus select distinct icons from ptca;
>
> Query 2
>
> select distinct icons from inpatient
> where icons NOT IN(select distinct icons from ptca)
>
> Query number one began to run in about 5 seconds whereas query 2 took
> forever to run. My question is why is the MINUS so much faster?
>
> My understanding of the NOT IN is that it probably builds the record set
in
> the second part of the SQL query each time it comes to a new icons number
in
> the first part of the query. Therefore, if there are one thousand records
to
> be searched, it probably builds the record set one thousand times. Is this
> correct? If so, how does the MINUS function build and compare the record
> set?
>
> And finally, where do I get these wonderful little tidbits? Would a SQL
> tuning book exist that might talk about the strengths and limitations of
> different functions? I really appreciate your time and input.
>
> Petre Hazelton
> Halifax, Nova Scotia CANADA
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Author: Saurabh Sharma
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