Comments on: SQL SERVER – Better Performance – LEFT JOIN or NOT IN?

By: Barbara70

Barbara70 — Sat, 10 Oct 2009 15:59:46 +0000

Thanks a lotI consider this site a very good one for me to face the interview questions ahead of me. ,

By: Pradip

Pradip — Tue, 06 Oct 2009 10:08:42 +0000

When you execute both query at one time it will show relative cost for each query.

By: Pradip

Pradip — Tue, 06 Oct 2009 09:00:42 +0000

I am not aware of how you measured resource percentage given “20% resources of execution plan and LEFT JOIN takes 80% resources of execution plan”. I need little more explanation.

Regards,
Pradip

By: Sam Rudolph

Sam Rudolph — Thu, 03 Sep 2009 10:30:57 +0000

hey Dave great thread, can you please tell me how did analyse the preform of the query,whats the meaning of 80% of the batch,and whats the tool you are using for the analysis??…
hope for the quick reply.
bbye

By: James

James — Tue, 30 Jun 2009 14:05:04 +0000

You are a star, three days of banging my head against the monitor have come to an end as a result of reading this post.

Thanks

By: kumar

kumar — Fri, 19 Jun 2009 11:08:00 +0000

Thanks a lot!!!

By: Matt

Matt — Fri, 12 Jun 2009 17:07:16 +0000

The difference is obvious in the query plans, the Join query is not using the index. You could alter the indices or the query to take advantage of the indices. Also, when you look at the statistics output you can see that the Join query is doing much better than the Not In query based on reads and scans, which in a high volume environment will be a much better indication of performance anyway. My opinion, the percentages shown on query plans are useless, use query plans only to figure out what indices you’re not taking advantage of (i.e. look for table and index scans).

By: brvcoordinator

brvcoordinator — Wed, 10 Jun 2009 16:04:27 +0000

Very Helpful!

By: Tiago Salgado

Tiago Salgado — Mon, 25 May 2009 08:43:05 +0000

Sanjay, you can use ROWCOUNT.

SET ROWCOUNT 10
SELECT * FROM table
SET ROWCOUNT 0

By: Sanjay

Sanjay — Tue, 17 Mar 2009 06:36:39 +0000

hi Pinal,

I want to retrieve only limited data from database like limit is keyword in mysql which retrieve limited data according to our arguments. Like I want to load only 10 records from the database at first display in page. but I don’t want to using top. Because its create problem of paging. So please give me alternate solution for that’d have use row index but in that row index I have to write inner query and my data base I s to heavy.

By: AK SABIN

AK SABIN — Fri, 27 Feb 2009 10:42:13 +0000

Brilliant posts !

By: ali

ali — Wed, 03 Dec 2008 09:33:59 +0000

–List names of authors who have contributed in
–any book title
SELECT DISTINCT authors.au_id,au_fname
FROM authors,titleauthor
WHERE authors.au_id!=titleauthor.au_id

SELECT au_id, au_fname FROM authors WHERE authors.au_id NOT IN
(SELECT au_id FROM titleauthor)

why the above query did not work as same as the below query??
the above on shows more records then the following.
why we did not do the same work with JOIN as with NOT IN??

By: Naseer Ahmad

Naseer Ahmad — Wed, 26 Nov 2008 12:56:06 +0000

Thanks for such a nice tip… its really help me in MySQL…

Thanks once again

regards,
Naseer Ahmad

By: Bob Zagars

Bob Zagars — Sat, 22 Nov 2008 04:40:22 +0000

Simple…KISS!

Oracle does not have Exists. Is there an equivalent?

Bob

By: Shantha

Shantha — Wed, 12 Nov 2008 12:33:50 +0000

Thanks! Really it is very useful for my query changes

By: jchen

jchen — Fri, 07 Nov 2008 22:39:29 +0000

I ran this select,
USE ttst
GO
SET SHOWPLAN_ALL ON
GO
select * from customer
where c.record_type = ‘T’
and c.customer_class_code = ‘LOCAL’
and c.customer_status_code = ‘ACTIVE’
SET SHOWPLAN_ALL OFF
GO
it gave me a error like below,
Server: Msg 1067, Level 15, State 1, Line 5
The SET SHOWPLAN statements must be the only statements in the batch.

(1 row(s) affected)
What is the correct way to use the set showplan_all on?

Jchen

By: Philihp

Philihp — Tue, 16 Sep 2008 03:53:50 +0000

Usually it is better to avoid correlated subselects. Looking only at only resources used is a pretty worthless method of evaluating optimization methods. The goal of optimization is to reduce run-time while still giving the correct answer.

By: Jerry Hung

Jerry Hung — Thu, 15 May 2008 14:19:04 +0000

NOT EXISTS/LEFT JOIN > SUBQUERY/NOT IN

That’s how I see it “most of the time”

By: Ronak

Ronak — Mon, 28 Apr 2008 06:02:18 +0000

Dude,

You know it well how query optimiser works. Do you work for MS cause noone can explain things like you.

By: SQL DBA

SQL DBA — Sun, 27 Apr 2008 06:00:45 +0000

Very very good.
Your explanations are great! Simply Great!