The reason the minus is so much faster is because it does a hash join. Try
adding a /*+ hash_aj */ hint to the "not in" and you should get better
response. Also, there is no need to put a distinct in the second select of
the minus or the sub select of the "not in". Minus will do a sort distinct
anyway. Here is the new sql.
select distinct icons
from inpatient
where icons not in (select /*+ hash_aj */ icons from ptca)
/
> -----Original Message-----
> From: Peter Hazelton [SMTP:[EMAIL PROTECTED]]
> Sent: Thursday, February 08, 2001 3:03 PM
> To: Multiple recipients of list ORACLE-L
> Subject: MINUS VS NOT IN
>
> 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: Peter Hazelton
> INET: [EMAIL PROTECTED]
>
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