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


Clustered Index


Clustered Index

Author
Message
maxyogesh2002
maxyogesh2002
SSC Rookie
SSC Rookie (42 reputation)SSC Rookie (42 reputation)SSC Rookie (42 reputation)SSC Rookie (42 reputation)SSC Rookie (42 reputation)SSC Rookie (42 reputation)SSC Rookie (42 reputation)SSC Rookie (42 reputation)

Group: General Forum Members
Points: 42 Visits: 108
Dear Friends

Is this true that Update SQL Query is slower because of Clustered index??????

currently i have cluster index on ID columns which have the primary key

How can i indentify the which column should have the Clustered index???

below i m attached my table defination...
Attachments
table_def.txt (35 views, 3.00 KB)
GilaMonster
GilaMonster
SSC-Forever
SSC-Forever (47K reputation)SSC-Forever (47K reputation)SSC-Forever (47K reputation)SSC-Forever (47K reputation)SSC-Forever (47K reputation)SSC-Forever (47K reputation)SSC-Forever (47K reputation)SSC-Forever (47K reputation)

Group: General Forum Members
Points: 47305 Visits: 44392
maxyogesh2002 (7/18/2009)
Is this true that Update SQL Query is slower because of Clustered index??????

Unlikely. Nonclustered indexes may slow a data modification down, because the change has to be made in multiple places, but that shouldn't be true of a clustered index because it's not a second copy of the data

currently i have cluster index on ID columns which have the primary key

How can i indentify the which column should have the Clustered index???


An identity's usually a fairly good choice for a cluster. It's narrow, unique and can't be changed plus the values for new rows are always higher than old, reducing fragmentation. I can't say if there's a better choice without knowing something about the data and how the table is used.


Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability

We walk in the dark places no others will enter
We stand on the bridge and no one may pass


maxyogesh2002
maxyogesh2002
SSC Rookie
SSC Rookie (42 reputation)SSC Rookie (42 reputation)SSC Rookie (42 reputation)SSC Rookie (42 reputation)SSC Rookie (42 reputation)SSC Rookie (42 reputation)SSC Rookie (42 reputation)SSC Rookie (42 reputation)

Group: General Forum Members
Points: 42 Visits: 108
i m attached the my table defined above...
Steve Jones
Steve Jones
SSC-Dedicated
SSC-Dedicated (36K reputation)SSC-Dedicated (36K reputation)SSC-Dedicated (36K reputation)SSC-Dedicated (36K reputation)SSC-Dedicated (36K reputation)SSC-Dedicated (36K reputation)SSC-Dedicated (36K reputation)SSC-Dedicated (36K reputation)

Group: Administrators
Points: 36224 Visits: 18751
The decision on what to make a clustered index is more based on the queries made against the table, not the definition. You would want those queries that look for a range of values, usually a date or other range to be considered. Typically I haven't picked the identity as the CI, but that's because I often have a better candidate, not because it's bad.

Follow me on Twitter: @way0utwest
Forum Etiquette: How to post data/code on a forum to get the best help
My Blog: www.voiceofthedba.com
Jeff Moden
Jeff Moden
SSC-Forever
SSC-Forever (45K reputation)SSC-Forever (45K reputation)SSC-Forever (45K reputation)SSC-Forever (45K reputation)SSC-Forever (45K reputation)SSC-Forever (45K reputation)SSC-Forever (45K reputation)SSC-Forever (45K reputation)

Group: General Forum Members
Points: 45207 Visits: 39925
First of all, that table is setup for CDR's (Call Detail Records). Rather I should say it's set up incorrectly for CDR's. Almost all of the columns are setup for VARCHAR(255) and the world of code is going to crawl because of all the implicit and explicit conversions you will need to make to rate, bill, and invoice the CDR's. Step 1 should be to assign the correct datatypes for each column.

Second... How often will you be inserting rows that are out of date order compared to what's at the "end" of the table? If it's a lot and your CI is on the date, you will get a lot of page splits. If it's a lot and your CI in on the autonumbering column, then you're inserts will be fine but your SELECT's may suffer a bit. It's a tradeoff depending on what the table will be used the most for... Inserts or Selects.

Are you going to use the contents of this table for rating and billing or are you just capturing CDR's for long term audits? And what's the source of information for this table? If it's coming directly from one or more switches as the calls occur, then you will definitely want the CI either on the IDENTITY column or on the call date time column.

No matter what, you really should fix the datatypes as previously stated.

--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.
Although they tell us that they want it real bad, our primary goal is to ensure that we dont actually give it to them that way.
Although change is inevitable, change for the better is not.
Just because you can do something in PowerShell, doesnt mean you should. Wink

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