Click here to monitor SSC
SQLServerCentral is supported by Redgate
 
Log in  ::  Register  ::  Not logged in
 
 
 


Wanting to learn. Who can best explain this in a simple yet crystal manner to a noob??


Wanting to learn. Who can best explain this in a simple yet crystal manner to a noob??

Author
Message
10e5x
10e5x
SSC-Enthusiastic
SSC-Enthusiastic (121 reputation)SSC-Enthusiastic (121 reputation)SSC-Enthusiastic (121 reputation)SSC-Enthusiastic (121 reputation)SSC-Enthusiastic (121 reputation)SSC-Enthusiastic (121 reputation)SSC-Enthusiastic (121 reputation)SSC-Enthusiastic (121 reputation)

Group: General Forum Members
Points: 121 Visits: 180
Hi all,

I am very new to T-SQL.. and i came across this:

ROW_NUMBER ( )
OVER ( [ PARTITION BY value_expression , ... [ n ] ] order_by_clause )

Can someone explain to me how this works, its purpose and when do we usually use it for?
Am i asking for knowledge and i am very confident some1 from this excellent forum explain this well.
anthony.green
anthony.green
SSCertifiable
SSCertifiable (6.1K reputation)SSCertifiable (6.1K reputation)SSCertifiable (6.1K reputation)SSCertifiable (6.1K reputation)SSCertifiable (6.1K reputation)SSCertifiable (6.1K reputation)SSCertifiable (6.1K reputation)SSCertifiable (6.1K reputation)

Group: General Forum Members
Points: 6106 Visits: 6078
Its a ranking function, which gives a list of rownumbers based on what you detail in the partitioning and ordering clauses.

The URL should explain it for you http://msdn.microsoft.com/en-us/library/ms186734.aspx



Want an answer fast? Try here
How to post data/code for the best help - Jeff Moden
When a question, really isn't a question - Jeff Smith
Need a string splitter, try this - Jeff Moden
How to post performance problems - Gail Shaw
CrossTabs-Part1 & Part2 - Jeff Moden
SQL Server Backup, Integrity Check, and Index and Statistics Maintenance - Ola Hallengren
Managing Transaction Logs - Gail Shaw
Troubleshooting SQL Server: A Guide for the Accidental DBA - Jonathan Kehayias and Ted Krueger


10e5x
10e5x
SSC-Enthusiastic
SSC-Enthusiastic (121 reputation)SSC-Enthusiastic (121 reputation)SSC-Enthusiastic (121 reputation)SSC-Enthusiastic (121 reputation)SSC-Enthusiastic (121 reputation)SSC-Enthusiastic (121 reputation)SSC-Enthusiastic (121 reputation)SSC-Enthusiastic (121 reputation)

Group: General Forum Members
Points: 121 Visits: 180
Thanks, yup i read that must still not as clear....
anthony.green
anthony.green
SSCertifiable
SSCertifiable (6.1K reputation)SSCertifiable (6.1K reputation)SSCertifiable (6.1K reputation)SSCertifiable (6.1K reputation)SSCertifiable (6.1K reputation)SSCertifiable (6.1K reputation)SSCertifiable (6.1K reputation)SSCertifiable (6.1K reputation)

Group: General Forum Members
Points: 6106 Visits: 6078
Can you explain which bits you are not clear on?



Want an answer fast? Try here
How to post data/code for the best help - Jeff Moden
When a question, really isn't a question - Jeff Smith
Need a string splitter, try this - Jeff Moden
How to post performance problems - Gail Shaw
CrossTabs-Part1 & Part2 - Jeff Moden
SQL Server Backup, Integrity Check, and Index and Statistics Maintenance - Ola Hallengren
Managing Transaction Logs - Gail Shaw
Troubleshooting SQL Server: A Guide for the Accidental DBA - Jonathan Kehayias and Ted Krueger


10e5x
10e5x
SSC-Enthusiastic
SSC-Enthusiastic (121 reputation)SSC-Enthusiastic (121 reputation)SSC-Enthusiastic (121 reputation)SSC-Enthusiastic (121 reputation)SSC-Enthusiastic (121 reputation)SSC-Enthusiastic (121 reputation)SSC-Enthusiastic (121 reputation)SSC-Enthusiastic (121 reputation)

Group: General Forum Members
Points: 121 Visits: 180
what does the partition does? and how does it affects the generating of row numbers. Does it have a similar function as GROUP BY?
anthony.green
anthony.green
SSCertifiable
SSCertifiable (6.1K reputation)SSCertifiable (6.1K reputation)SSCertifiable (6.1K reputation)SSCertifiable (6.1K reputation)SSCertifiable (6.1K reputation)SSCertifiable (6.1K reputation)SSCertifiable (6.1K reputation)SSCertifiable (6.1K reputation)

Group: General Forum Members
Points: 6106 Visits: 6078
The partition will restart the row number based on that you detail.

So in the examples on the MSDN article, Example C uses partition, so that you can see the top person per region.

So if you look at the output, you will see its not a sequential series of numbers in the row_number column, it goes 1,2,3,1,1,1,1,2,1,2,3,4 etc and you can see that it restarts the row number for reach region.

So then the person can just say get me everyone where row number = 1 to get the top sales person for each region.

There is no group by for ROW_NUMBER as it is a ranking function and will always generate a unique row so you wont be able to group the data, that should be done before using row number.



Want an answer fast? Try here
How to post data/code for the best help - Jeff Moden
When a question, really isn't a question - Jeff Smith
Need a string splitter, try this - Jeff Moden
How to post performance problems - Gail Shaw
CrossTabs-Part1 & Part2 - Jeff Moden
SQL Server Backup, Integrity Check, and Index and Statistics Maintenance - Ola Hallengren
Managing Transaction Logs - Gail Shaw
Troubleshooting SQL Server: A Guide for the Accidental DBA - Jonathan Kehayias and Ted Krueger


10e5x
10e5x
SSC-Enthusiastic
SSC-Enthusiastic (121 reputation)SSC-Enthusiastic (121 reputation)SSC-Enthusiastic (121 reputation)SSC-Enthusiastic (121 reputation)SSC-Enthusiastic (121 reputation)SSC-Enthusiastic (121 reputation)SSC-Enthusiastic (121 reputation)SSC-Enthusiastic (121 reputation)

Group: General Forum Members
Points: 121 Visits: 180
Oh ok thanks... i uds leWink
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