One of the basic Database Rule I have is that all the table must Clustered Index. Clustered Index speeds up performance of the query ran on that table. Clustered Index are usually Primary Key but not necessarily. I frequently run following query to verify that all the Jr. DBAs are creating all the tables with Clustered Index.
USE AdventureWorks ----Replace AdventureWorks with your DBName
GO
SELECT DISTINCT [TABLE] = OBJECT_NAME(OBJECT_ID)
FROM SYS.INDEXES
WHERE INDEX_ID = 0
AND OBJECTPROPERTY(OBJECT_ID,'IsUserTable') = 1
ORDER BY [TABLE]
GO
Result set for AdventureWorks:
TABLE
——————————————————-
DatabaseLog
ProductProductPhoto
(2 row(s) affected)
Related Post:
SQL SERVER – 2005 – Find Tables With Primary Key Constraint in Database
SQL SERVER – 2005 – Find Tables With Foreign Key Constraint in Database
Reference : Pinal Dave (http://blog.SQLAuthority.com) , BOL
I have a table with Huge number of records. Is it advisable to have Clustered Index On it?
hi,
i’ve another question, i want to use this query in sql 2000, its not working with the above mentioned query kindly advise the update, will appreciate your quick response
what is query for finding primary key from the table ?
i have only table.
Kalpesh,
Good Question, I will write query tonight and post it tomorrow. Please check the blog tomorrow.
Regards,
Pinal Dave ( http://www.SQLAuthority.com )
[...] 4th, 2007 by pinaldave While writing article based on my SQL SERVER – 2005 Find Table without Clustered Index – Find Table with no Primary Key I got idea about writing this article. I was thinking if you can find primary key for any table in [...]
[...] 4th, 2007 by pinaldave My article SQL SERVER – 2005 Find Table without Clustered Index – Find Table with no Primary Key has received following question many times. I have deleted similar questions and kept only latest [...]
At what point do you recommend to recompute statistics on the indexes in the table? Is it advisable to have a job which will recompute the statistics on the table after xxx number of records have got inserted?
Srinivasan Prasanna,
I recompute statistics every night when we have very low usage of database. It is not recommended to compute based on some specific amount of rows are inserted because, it may be possible Server is very busy and will have degraded performance or may have lots of deadlocks.
Regards,
Pinal Dave ( http://www.SQLAuthority.com )
Dave,
Why the insistence on a clustered index as opposed to a non-clustered index? My understanding is that a clustered index actually orders the physical table based on the index field while non-clustered indexes do not. Would there be a cost associated with this as well( ie. slower updates, inserts )?
Thanks
Clustered Index improves performance.
(correct me if I’m wrong, all)
Brad, yes there is a cost, but frequently the cost during the insert is paid back by all the subsequent . Say you have a clustered index by date. Say you need to add some records from yesterday. Depending on how many, as well as the standard % of space in the index, in order to put the data in the index you might have to shift pages down, which would impact performance. But, except in high-transaction environments, this is usually not an issue – just make sure to leave room in the index, and don’t do something like use a random number (or GUID) as the key.
Dave,
I have the same question as – 1 Sham
I have a table with Huge number of records. Is it advisable to have Clustered Index On it?
Hi, I disagree with your statement that all tables must have a clustered index, I have practical prove that it only enhances performance on tables that have very low insert, deletes and updates on the column that has the clustered index, and if you have lots of delete and updates on these tables the performance actually decreses.
If you really understand the concept of clustered indexes you find the answer. Clustered indexes order the phisical data table on the index key order, that means, instead of having another table with only the index key and the pointer, sql server has to order the whole data table based on the key order, and that translates to lots of I/O and lots of locks on the table, and that of course for tables that have frequent updates and deletes.
But if you have very low updates and deletes on this table, clustered indexes really increase performance.
what is primary key clustered??? and unique non clustered???
Is there is any way to fetch the Unique index key columns if we knows the database name ?
I want 2 know which type of index is applied on table .
there is no key applied on that table …
pls helpme
Guyes,
I want to know the F4 (search for objects) procedures in 2005. How to do that?
Thaks
how many unique key have in a table?
hi,
what is the diff between cluster/non cluster index?
Hi,
Could you please tell me the scenario in which i should opt for custered index or non-clustered index. What is the trade off between two?
first of all we have to look into our requirements. if we are working with database with lots of read (reporting server or olap db) then having a cluster index is a must. but if we are having lots of writes eg. table is working as temp table to store data then non cluster indexes can give better performance. but for important table , having cluster index is very important.
I want to find out tables in my database who are using indexes. So that i could create similar indexes on the copy of the databse.
@shashi,
Follow this link, there is a already written script which you can refer to, this script will create a script for all indexes in the database, including primary key and unique key indexes.
http://www.sqlservercentral.com/scripts/Index+Management/31652/
If link does not works, do this,
go to google.com, type “how to script all indexes in a database sql server” and click the first link.
Hope this helps.
Imran.
Dave, you are propagating a dangerous generalization with this blog post and subsequent comments. DBAs and database developers need to have an in-depth understanding of SQL Server in order to comprehend the implications of creating any type of index. Clustered indices CAN enhance performance, but they come with many trade-offs. For example:
- a poorly-chosen clustered index key can provoke table scans where an effective one will enable seeks, especially in the case of range queries.
- a poor clustered index will definitely result in a high rate of table and index fragmentation, as alluded to by Marco C above.
- the clustered index key is implicitly included in all non-clustered indices, so choosing one that is too wide will slow performance and increase the size of all non-clustered indices on the same table.
So saying things like “Clustered Index improves performance,” as you do in the comments, is a bad idea. I urge you to review your understanding of SQL Server data structures so that you do not promote potentially damaging ideas in your role as a Microsoft MVP.
Hi,
Can you please guide me how to find record which are not inserted in index.
[...] SQL SERVER – 2005 Find Table without Clustered Index – Find Table with no Primary Key [...]
Is their any simplest way to find table dependancies….
I want to find a particular table is dependant on which other table in database.
@Pankaj,
You can try one of these,
1. SP_depends [object_name]
2. SP_help [object_name]
3. From SQL Server Management Studio, in Object Explorer, right click Table Name – View dependencies.
~ IM.
hi
i have converted non clustered index to clustered index
by using the below query
create unique clustered index PK_Activity on Activity(Activity_id) WITH DROP_EXISTING
some times it is not working because the table have
foreign key
how to avoid the foreign key problem
@sourirajan
What do you mean by Not working.
What is not working. Please provide more details.
~ IM.
Hi Pinal,
I am a developer from pvt. firm in navi mumbai. I am developing an application which will handle entire email server transactions by an IT person. To develop this application using .net 2008 and Sql server 2005, i have 2 tables having records 2,500,000+ and 150,000+ respectively in its initial stage which will grow to 10 folds possibly in future. I want to have search queries on these tables to show updates through this application. WIth this table i have 3 more tables having records less than 35000 each which will be used with inner joins to display specific info on application.
Now , i want your help on how should i design queries or indexes which will fetch me desired results without giving connection timeout error. And also it should not take considerable time to load.My seniors have challenged me to fix this issue. I dont want to keep anything for them from my side. So please help me on this.
Please reply me on above email id by or before monday so i shold progress asap on this development.
Hi All,
I going through the implementation of indexes on following given table and will use following reterival queries to retreive the data. Can you please help me out which column(s) I should use for Clustered index & for Non Clustered and for Included Columns index for covered queries.. with example..
–Table Defination starts–
Create Table tblNews
(
SectionID int,
NewsID int,
Headline varchar(500),
Short_Story varchar(500),
PublishDate DateTime,
CONSTRAINT pk_NewsID Primary Key (NewsID)
)
–Table Defination ends–
–Queries—
select Headline, Short_Story from tblNews order by PublishDate desc
select Headline, Short_Story from tblNews where SectionID=1 order by PublishDate desc
select Headline, Short_Story from tblNews where NewsID between 1000 and 1500
select Headline, Short_Story from tblNews where Headline like ‘%USA%’order by PublishDate desc
—-
Please do suggest and it will be a great help.
Thanks
Gaurav Kukar
Hello Pinal,
I was given database. They added some tables. And I need to improve database optimization of table. What is the best way to start and what other things it requires?
Thanks,
Krunal
Hi Gaurav Kukar,
I think you need non-clustered index on the following fields:
PublishDate
SectionID
Headline
Please correct me Pinal if I am wrong.
Thanks.
hi
i want to find out non-cluster index applied to column in that table
how it is possible
can you guide me please
Regards
sharad
hi Pinal,
I am having records of 1 lakh and i have to retrive date on search .So i want improve its performance.Is it would be good idea going for clustered index?.
Thanks and regards,
lokesh
Hi Dave,
There is another way to achieve this:
select NAME
FROM sys.tables
WHERE OBJECTPROPERTY([OBJECT_ID],’TableHasClustIndex’) =0
ORDER BY name ASC
And, if you want to return the schema too, you can run :
SELECT T.name AS TABLE_NAME , S.name AS SCHEMA_NAME
FROM sys.tables T
INNER JOIN sys.schemas S
on S.schema_id = T.schema_id
WHERE OBJECTPROPERTY([OBJECT_ID],’TableHasClustIndex’) =0
ORDER BY S.name,T.name ASC
can we create non clustered index on table which do not have a clustered index??
please send mr response..
Yes it is possible. Did you try?
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