SQL Clone
SQLServerCentral is supported by Redgate
 
Log in  ::  Register  ::  Not logged in
 
 
 


Which is Better?


Which is Better?

Author
Message
AndrewSQLDBA
AndrewSQLDBA
SSCommitted
SSCommitted (1.8K reputation)SSCommitted (1.8K reputation)SSCommitted (1.8K reputation)SSCommitted (1.8K reputation)SSCommitted (1.8K reputation)SSCommitted (1.8K reputation)SSCommitted (1.8K reputation)SSCommitted (1.8K reputation)

Group: General Forum Members
Points: 1752 Visits: 3427
Hello Everyone
I am reviewing code in a SQL database that was coded by a BA and a Old oracle developer. Never a good idea to begin with. I am finding a lot of queries that should be using a JOIN, or LEFT OUTER JOIN, and they are using sub-queries with NOT IN. Plus s lot of just poorly written code.

I am looking for some solid proof as to which type of query is better. I have always known that using JOIN is always better for performance since one can index that column(s) that the JOIN will use. Which is usually a Primary key in the tables involved.

Can someone shed some light on this.

Thank you in advance for all your advice, suggestions and time.

Andrew SQLDBA
Keith Tate
Keith Tate
Ten Centuries
Ten Centuries (1K reputation)Ten Centuries (1K reputation)Ten Centuries (1K reputation)Ten Centuries (1K reputation)Ten Centuries (1K reputation)Ten Centuries (1K reputation)Ten Centuries (1K reputation)Ten Centuries (1K reputation)

Group: General Forum Members
Points: 1012 Visits: 979
Aaron Bertrand has a great article on this topic http://www.sqlperformance.com/2012/12/t-sql-queries/left-anti-semi-join



Microsoft Certified Master - SQL Server 2008
Follow me on twitter: @keith_tate

Forum Etiquette: How to post data/code on a forum to get the best help
Jeff Moden
Jeff Moden
SSC Guru
SSC Guru (84K reputation)SSC Guru (84K reputation)SSC Guru (84K reputation)SSC Guru (84K reputation)SSC Guru (84K reputation)SSC Guru (84K reputation)SSC Guru (84K reputation)SSC Guru (84K reputation)

Group: General Forum Members
Points: 84679 Visits: 41069
AndrewSQLDBA (4/14/2014)
Hello Everyone
I am reviewing code in a SQL database that was coded by a BA and a Old oracle developer. Never a good idea to begin with. I am finding a lot of queries that should be using a JOIN, or LEFT OUTER JOIN, and they are using sub-queries with NOT IN. Plus s lot of just poorly written code.

I am looking for some solid proof as to which type of query is better. I have always known that using JOIN is always better for performance since one can index that column(s) that the JOIN will use. Which is usually a Primary key in the tables involved.

Can someone shed some light on this.

Thank you in advance for all your advice, suggestions and time.

Andrew SQLDBA


To be honest, IN and NOT IN are actually a little bit faster than the related joins. There are some caveates for both that people need to understand. NOT IN can actually be a fair bit faster than an OUTER JOIN with a predicate that looks for NULLs.

--Jeff Moden

RBAR is pronounced ree-bar and is a Modenism for Row-By-Agonizing-Row.
First step towards the paradigm shift of writing Set Based code:
Stop thinking about what you want to do to a row... think, instead, of what you want to do to a column.
If you think its expensive to hire a professional to do the job, wait until you hire an amateur. -- Red Adair

Helpful Links:
How to post code problems
How to post performance problems
Forum FAQs
AndrewSQLDBA
AndrewSQLDBA
SSCommitted
SSCommitted (1.8K reputation)SSCommitted (1.8K reputation)SSCommitted (1.8K reputation)SSCommitted (1.8K reputation)SSCommitted (1.8K reputation)SSCommitted (1.8K reputation)SSCommitted (1.8K reputation)SSCommitted (1.8K reputation)

Group: General Forum Members
Points: 1752 Visits: 3427
Thank you to you both.

I read the article, that is a very good one.

Thanks again
Andrew SQLDBA
Jeff Moden
Jeff Moden
SSC Guru
SSC Guru (84K reputation)SSC Guru (84K reputation)SSC Guru (84K reputation)SSC Guru (84K reputation)SSC Guru (84K reputation)SSC Guru (84K reputation)SSC Guru (84K reputation)SSC Guru (84K reputation)

Group: General Forum Members
Points: 84679 Visits: 41069
Here's another excellent link on the subject. The article also has other links. Gail Shaw is a Microsoft Certified Master and she has put together quite the writeup on these subjects including some of the caveates of using one vs another.

http://sqlinthewild.co.za/index.php/2010/02/18/not-exists-vs-not-in/

--Jeff Moden

RBAR is pronounced ree-bar and is a Modenism for Row-By-Agonizing-Row.
First step towards the paradigm shift of writing Set Based code:
Stop thinking about what you want to do to a row... think, instead, of what you want to do to a column.
If you think its expensive to hire a professional to do the job, wait until you hire an amateur. -- Red Adair

Helpful Links:
How to post code problems
How to post performance problems
Forum FAQs
Go


Permissions

You can't post new topics.
You can't post topic replies.
You can't post new polls.
You can't post replies to polls.
You can't edit your own topics.
You can't delete your own topics.
You can't edit other topics.
You can't delete other topics.
You can't edit your own posts.
You can't edit other posts.
You can't delete your own posts.
You can't delete other posts.
You can't post events.
You can't edit your own events.
You can't edit other events.
You can't delete your own events.
You can't delete other events.
You can't send private messages.
You can't send emails.
You can read topics.
You can't vote in polls.
You can't upload attachments.
You can download attachments.
You can't post HTML code.
You can't edit HTML code.
You can't post IFCode.
You can't post JavaScript.
You can post emoticons.
You can't post or upload images.

Select a forum

































































































































































SQLServerCentral


Search