Advantages Of Using Nonclustered Index After Using Clustered Index On One Table
Jul 3, 2006
Hi everyone,
When we create a clustered index firstly, and then is it advantageous to create another index which is nonclustered ??
In my opinion, yes it is. Because, since we use clustered index first, our rows are sorted and so while using nonclustered index on this data file, finding adress of the record on this sorted data is really easier than finding adress of the record on unsorted data, is not it ??
Thanks
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Apr 1, 2006
Hello I want to learn disparity clustered index or nonclustered index and in queries which one run better.
example
select * from orders where orderID=5
to this query clustered or nonclustered
thanks
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Feb 20, 2004
I have 3 table A, B, C
Table A (15 field, 4 fields indexed and Primary Key) – approximate rows: 50.000 – 60.000
Table B (18 field, 6 fields indexed and Primary Key) – approximate rows: 350.000 – 500.000
Table C (16 filed, 9 fields indexed and Primary Key) – approximate rows: 500.000 – 1.000.000
Structure is something like this:
A (master) --> B (detail) ---> C (sub detail)
On each 3 table is added new record, in table C the record is added after a search in table B.
My question is: Which is the best method? CLUSTERED INDEX or NONCLUSTERED INDEX
Thanks
Sorry for my english
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Jun 2, 2006
when do you use them?
i only know you use clustered when you have million of records. So once the table has been indexed, query statement is able to retrieve the recordset faster.
what about nonclustered?
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Nov 14, 2006
the query:
SELECT a.AssetGuid, a.Name, a.LocationGuid
FROM Asset a WHERE a.AssociationGuid IN (
SELECT ada.DataAssociationGuid FROM AssociationDataAssociation ada
WHERE ada.AssociationGuid = '568B40AD-5133-4237-9F3C-F8EA9D472662')
takes 30-60 seconds to run on my machine, due to a clustered index scan on our an index on asset [about half a million rows]. For this particular association less than 50 rows are returned.
expanding the inner select into a list of guids the query runs instantly:
SELECT a.AssetGuid, a.Name, a.LocationGuid
FROM Asset a WHERE a.AssociationGuid IN (
'0F9C1654-9FAC-45FC-9997-5EBDAD21A4B4',
'52C616C0-C4C5-45F4-B691-7FA83462CA34',
'C95A6669-D6D1-460A-BC2F-C0F6756A234D')
It runs instantly because of doing a clustered index seek [on the same index as the previous query] instead of a scan. The index in question IX_Asset_AssociationGuid is a nonclustered index on Asset.AssociationGuid.
The tables involved:
Asset, represents an asset. Primary key is AssetGuid, there is an index/FK on Asset.AssociationGuid. The asset table has 28 columns or so...
Association, kind of like a place, associations exist in a tree where one association can contain any number of child associations. Each association has a ParentAssociationGuid pointing to its parent. Only leaf associations contain assets.
AssociationDataAssociation, a table consisting of two columns, AssociationGuid, DataAssociationGuid. This is a table used to quickly find leaf associations [DataAssociationGuid] beneath a particular association [AssociationGuid]. In the above case the inner select () returns 3 rows.
I'd include .sqlplan files or screenshots, but I don't see a way to attach them.
I understand I can specify to use the index manually [and this also runs instantly], but for such a simple query it is peculiar it is necesscary. This is the query with the index specified manually:
SELECT a.AssetGuid, a.Name, a.LocationGuid
FROM Asset a WITH (INDEX (IX_Asset_AssociationGuid)) WHERE
a.AssociationGuid IN (
SELECT ada.DataAssociationGuid FROM AssociationDataAssociation ada
WHERE ada.AssociationGuid = '568B40AD-5133-4237-9F3C-F8EA9D472662')
To repeat/clarify my question, why might this not be doing a clustered index seek with the first query?
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Aug 28, 2015
I desire to have a clustered index on a column other than the Primary Key. I have a few junction tables that I may want to alter, create table, or ...
I have practiced with an example table that is not really a junction table. It is just a table I decided to use for practice. When I execute the script, it seems to do everything I expect. For instance, there are not any constraints but there are indexes. The PK is the correct column.
CREATE TABLE [dbo].[tblNotificationMgr](
[NotificationMgrKey] [int] IDENTITY(1,1) NOT NULL,
[ContactKey] [int] NOT NULL,
[EventTypeEnum] [tinyint] NOT NULL,
[code]....
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Jan 4, 2008
I have large table with 10million records. I would like to create clustered or non-clustered index.
What is the quick way to create? I have tried once and it took more than 10 min.
please help.
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Dec 5, 2007
Dear All.
We had Teradata 4700 SMP. We have moved data from TD to MS_SQL SERVER 2003. records are 19.65 Millions.
table is >> Order_Dtl
Columns are:-
Client_ID varchar 10
Order_ID varchar 50
Order_Sub_ID decimal
.....
...
..
.
Pk is (ClientID+OrderId+OrderSubID)
Web Base application or PDA devices use to initiate the order from all over the country. The issue is this table is not Partioned but good HP with 30 GB RAM is installed. this is main table that receive 18,0000 hits or more. All brokers and users are using this table to see the status of their order.
The always search by OrderID, or ClientID or order_SubNo, or enter any two like (Client_ID+Order_Sub_ID) or any combination.
Query takes to much time when ever server receive more querys. some orther indexes are also created on the same table like (OrderDate, OrdCreate Date and Status)
My Question are:-
Q1. IF Person "A" query to DB on Client_ID, then what Index will use ? (If any one do Query on any two combination like Client_ID+Order_ID, So what index will be uesd.? How does MS-SQL SERVER deal with these kind of issues.?
Q2. If i create 3 more indexes on ClientID, ORderID and OrdersubID. will this improve the performance of query.if person "A" search record on orderNo so what index will be used. (Mind it their would be 3 seprate indexes for Each PK columns) and composite-Clustered index is also available.?
Q3. I want to check what indexes has been used? on what search?
Q4. How can i check what table was populated when, or last date of update (DML)?
My Limitation is i Dont Create a Partioned table. I dont have permission to do it.
In Teradata we had more than 4 tb record of CRM data with no issue. i am not new baby in db line but not expert in sql server 2003.
I am thank u to all who read or reply.
Arshad
Manager Database
Esoulconsultancy.com
(Teradata Master)
10g OCP
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Mar 5, 2015
I have a clustered index that consists of 3 int columns in this order: DateKey, LocationKey, ItemKey (there are many other columns in this data warehouse table such as quantities, prices, etc.).
Now I want to add a non-clustered index on just one of the other columns, say LocationKey, like this:
CREATE INDEX IX_test on TableName (LocationKey)
I understand that the clustered index keys will also be added as key columns to any NC indexes. So, in this case the NC index will also get the other two columns from the clustered index added as key columns. But, in what order will they be added?
Will the resulting index keys on this new NC index effectively be:
LocationKey, DateKey, ItemKey
OR
LocationKey, ItemKey, DateKey
Do the clustering keys get added to a NC index in the same order as they are defined in the clustered index?
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Jun 18, 2008
Quick question about the primary purpose of Full Text Index vs. Clustered Index.
The Full Text Index has the purpose of being accessible outside of the database so users can query the tables and columns it needs while being linked to other databases and tables within the SQL Server instance.
Is the Full Text Index similar to the global variable in programming where the scope lies outside of the tables and database itself?
I understand the clustered index is created for each table and most likely accessed within the user schema who have access to the database.
Is this correct?
I am kind of confused on why you would use full text index as opposed to clustered index.
Thank you
Goldmember
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Nov 19, 1999
hello!
Is it possible to set nonclustered
index on column with dublicate values?
Thank you,
Alona
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Jul 6, 2007
Hi guys. I have a table named [Check] and need to create an index for CVNumber field. The table has no primary key for the meantime. I tried this script but error occured.
BEGIN TRANSACTION
SET QUOTED_IDENTIFIER ON
GO
SET TRANSACTION ISOLATION LEVEL SERIALIZABLE
GO
COMMIT
BEGIN TRANSACTION
CREATE NONCLUSTERED INDEX IX_Check_1 ON dbo.[Check]
(
CVNumber
) ON [PRIMARY]
GO
COMMIT
Error message:
Server: Msg 3023, Level 16, State 2, Line 3
Backup, CHECKALLOC, bulk copy, SELECT INTO, and file manipulation (such as CREATE FILE) operations on a database must be serialized. Reissue the statement after the current backup, CHECKALLOC, or file manipulation operation is completed.
Server: Msg 3902, Level 16, State 1, Line 1
The COMMIT TRANSACTION request has no corresponding BEGIN TRANSACTION.
Is it because I used the table name Check which is a reserved word for SQL? But I included [ ].
Please help. Thank you.
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Jul 18, 2006
Hi everyone,
I have some problems on composite nonclustered indexes. I could not exatly understand their logic.
In my opininon, suppose that we have a table called Order and we create a composite nonclustered index on this table for OrderID column and OrderDate column. So I am using this query;
SELECT * FROM Order WHERE OrderID > 12 ORDER BY OrderDate
So in here, I think our first research is based on OrderID and ten after ordering our data pointer according to the OrderID and then our index is converted to an index which is based on OrderDate while performing ordering. So is this correct ??
Would you please explain this ?
Thanks
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Oct 28, 2006
I already posted this over on sqlteam so don't peek there if you haven't seen that post yet. :)
So now to the question:
Anyone care to guess how long it took me to build a clustered index on a table with 900 million rows? This is the largest amount of data in a single table I have had to work with thus far in my career! It's sorta fun to work with such large datasets. :)
Some details:
1. running sql 2005 on a dual proc 32bit server, 8gb ram, hyperthreaded, 3ghz clock. disk is a decent SAN, not sure of the specs though.
2. ddl for table:
CREATE TABLE [dbo].[fld](
[id] [bigint] NOT NULL,
[id2] [tinyint] NOT NULL,
[extid] [bigint] NOT NULL,
[dd] [bit] NOT NULL,
[mp] [tinyint] NOT NULL,
[ss] [tinyint] NOT NULL,
[cc] [datetime] NOT NULL,
[ff] [tinyint] NOT NULL,
[mm] [smallint] NOT NULL,
[ds] [smallint] NOT NULL
)
3. ddl for index (this is the only index on the table):
CREATE CLUSTERED INDEX [CIfld]
ON [dbo].[fld]
(
extid asc
)WITH (FILLFACTOR=100, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF)
4. extid column was not sorted to begin with. ordering was completely random.
Note that I have changed the column names, etc, to protect the innocent. I can't go into details about what it's for or I'd be violating NDA type stuff.
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Jul 23, 2005
When a nonunique nonclustered index is built on top of a clusteredindex, is it guaranteed that the bookmark in the nonclustered indexwill be kept in the same order as the clustered index?Here's an example to demonstrate my question:CREATE TABLE indextest (col1 int NOT NULL,col2 int NOT NULL,col3int,col4 int)ALTER TABLE indextest ADD PRIMARY KEY CLUSTERED (col1,col2)CREATE INDEX ix_indextest ON indextest (col1,col3)GOINSERT indextest VALUES (1,2,1,1)INSERT indextest VALUES (1,3,2,1)INSERT indextest VALUES (1,4,2,1)INSERT indextest VALUES (2,1,1,1)INSERT indextest VALUES (1,1,1,1)SELECT col1,col2 FROM indextest WHERE col1=1 AND col3=1DROP TABLE indextestThe select statement above is covered by the nonclustered index, sothat index is used. However, the nonclustered index is defined only toensure the ordering of col1 and col3 within the index; col1 and col2follow within the index as the bookmark to the clustered index. When Irun this query, my desired result is to have the records appear in theorder supported by the clustered index:1,11,2As it happens, the result I got was indeed in that order, but I don'tknow if it was mere coincidence, or if the bookmark in the nonclusteredindex is maintained in the same order as the clustered index. If Iwant to ensure the above order, is it sufficient to have thenonclustered index defined as above, or do I need to define it as:create index ix_indextest on indextest (col1,col3,col2)just to be sure that the results are returned in ascending order forcol1,col2? If the two-column index is sufficient, is it guaranteed tostill be sufficient in SQL2005 and future versions of SQL Server, or amI better off adding the third column just to be safe?Thank you,--Dennis Culley
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Aug 27, 2015
I have table which having clustered index based on column (A,B,C,D,E,F).Now my query based on B,D,F. e.g: where b='Test1' and D='test2' and F='test3' Now Execution plan ask to create non clustered index with (B,D,F) column.is it make any sense to create non clustered index where clustered already available.
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Dec 3, 2007
I am attempting to understand the behaviour of a nonclustered index in regards to page splitting.
If I had the following table:-
Col1, Col2, Value
This table has a Clustered index on Col1, Col2 and a NonClustered index on Col2 and include Col1, Values.
If inserts into Col1 were causing page splits in the Clustered index, what are the effects on the NonClustered index?
I am attempting to understand what happens to the NonClustered index in this scenario so that I can make a decision on what fillfactor to use.
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Mar 22, 2001
We are trying to load flat text files with upwards of 7 million records into a table on SQL. The table has a clustered index on 3 fields. We setup the indexes prior to importing the data. We are sometimes able to complete smaller tables (500,000-750,000 records), however when we try the larger tables an error occurs :
Error at Destination for row number 6785496. Errors encountered so far in this task: 1
Location: somerge.c:1573
Expression: mrP->mrStatus!=MERGERUN::NONE
SPID: 11
Process ID: 173
The destination row number is the same number as the total number of rows that we are trying to load.
None of the recods end up importing. The row number it gives is always the total number of records that was in the text file I was trying to import. I tried to import the text files first and then build the clustered indexes but a table with only 300,000 records ran for nearly 4 days without completing before we killed it.
Be for we try to load the file we always delete whatever is there. Some of the files that we try to load are new and we have to set up the indexes from scratch.
We are using a DTS wizard. Someone told me to find a way to get it to commit every 1000 or so but I can't find a way to do it. I looked and looked but can't find it !!!
Please help me on where to look......:(
Thanks,
Cheri
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Oct 31, 2015
Give a user table MyTable. How to know whether the table contains a non-unique clustered index by using SQL query?
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Nov 14, 2007
Hi all
as i remember i had read in Books Online that on each Table in Sql Server we can create only one Clustered index
but today suddenly i create another clustered index on a table without any Error from SQl server !!!
BUT my query Order changed to the order of this newly created index.
could anyone elaborate on this issue?
Thanks in advance.
Regards.
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Feb 29, 2008
I have a table "Client" that has two columns: "ClientID" and "ProductID". I created on clustered index on ClientID and when I opened the table in the management studio, I saw the table was in the order of ClientID.
Then I added another non-clustered index on ProductID. When I open the table again, it is in the order of ProductID. Shouldn't the table always be in the order of clustered index? Non-clustered index should be a structure outside of the table itself? Did I do anything wrong?
Thanks for any hint.
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Oct 15, 2007
Hi everybody!
I just ran the Database Engine Tuning Advisor on a relative complex query to find out if a new index might help, and in fact it found a combination that should give a performance gain of 94%. Fair enough to try that.
What I wonder about: The index I should create contains 4 columns, the last of them being the Primary Key column of the table, which is also my clustered index for the table. It is an identity integer btw.
I think I remember that ANY index does include the clustered one as lookup into the data, so having it listed to the list of columns will not help. It might at worst add another duplicate 4 bytes to each index entry.
Right? Wrong? Keep the column in the index, or remove it since it is included implicit anyway?
Thanks for suggestions!
Ralf
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Nov 2, 2010
I am trying to create a temp table with a non-clustered index.
Originally I tried to create the index after I created the table.
This seemed to work fine, so I added my stored procedure to our Production environment.
However, when two users called the stored procedure at once I got the following error:
There is already an object named 'IX_tmpTableName' in the database. Could not create constraint. See previous errors.
I then found that SQL Server does generate unique names for the temp table but not all the objects associated with the temp table if they are explicitly named.
This is easy enough to solve for a PRIMAY KEY or UNIQUE constraint because the do not have to be named.
Is there a way to create an non-clustered index on a temp table without naming it?
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Oct 31, 2015
Give a user table ‘MyTable’. How to know whether the table contains a non-unique clustered index by using SQL query?
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Jan 17, 2008
My environment is SQL 2000. I have a table with 500 million rows. The table is consistently getting updated and inserted. I can not take the table offline. My clustered index needs to be rebuilt due to decreased performance. How do I accomplish this?
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Mar 28, 2014
I have a table with clustered index on that. I have only 5 columns in that table. Execution plan is showing that Index scan occurred. What are the cause of the Index scan how can we change that to index seek?
I am giving that kind of similar query below
SELECT @ProductID= ProductID FROM Product WITH (NOLOCK) WHERE SalesID= '@salesId' and Product = 'Clothes '
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May 7, 2014
I need to create a Clustered Index (CI) on a very large SQL Server 2012 database table. This table has about approximately 10 billion rows, 500 GB in size. The job ran for about 20 hours into it and then fails with error: "Out of disk space in tempdb". My tempDB size is 1.8TB, but yet it's still not enough.
Here is my script:
CREATE CLUSTERED INDEX CI_IndexName
ON TableName(Column1,Column2)
WITH (MAXDOP= 4, ONLINE=ON, SORT_IN_TEMPDB = ON, DATA_COMPRESSION=PAGE)
ON sh_WeekDT(Day_DT)
GO
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Mar 7, 2015
I have three sprocs and three tables. I was told to use a clustered index in the first table and a unique clustered index on the second table. I never asked about the third table and the person I need to ask is on vacation. Most of the contents of the first table will be joined with all of the contents of the second table into the third table. Do I need to have a unique clustered index on the third table too?
The clustered index in the first sproc is on a unique key that I had created using by concatenating several columns together.
CREATE CLUSTERED INDEX IX_UNIQUE_KEY ON MRP.Margin_Optimization_Data (UNIQUE_KEY);
CREATE NONCLUSTERED INDEX IX_DATE ON MRP.Margin_Optimization_Data (PERIOD);
CREATE NONCLUSTERED INDEX IX_ODS_ID ON MRP.Margin_Optimization_Data
(GL_SEG1_COMPANY_ODS_ID, GL_SEG2_PROFIT_CTR_ODS_ID, GL_SEG3_LOB_ODS_ID, GL_SEG4_PRODUCT_DEPT_ODS_ID, GL_SEG5_ACCOUNT_ODS_ID);
The second sproc with the unique clustered index is on the unique key from the first table and a date attribute.
CREATE UNIQUE CLUSTERED INDEX IX_UNIQUE_KEY ON MRP.[MGN_OPT_KPI_SOURCE] (UNIQUE_KEY, PERIOD);
In the third sproc, I'll have a nonclusted index on the ODS_ID attributes, but I'm unsure of how to go about the clustered index situation.
CREATE NONCLUSTERED INDEX IX_ODS_ID ON MRP.MGN_OPT_KPI_VALUES
(GL_SEG1_COMPANY_ODS_ID, GL_SEG2_PROFIT_CTR_ODS_ID, GL_SEG3_LOB_ODS_ID, GL_SEG4_PRODUCT_DEPT_ODS_ID, GL_SEG5_ACCOUNT_ODS_ID);
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Oct 30, 2015
Give a user table ‘MyTable’. How to know whether the table contains a non-unique clustered index by using SQL query?
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Jun 3, 2014
I was under impression that rebuilding index online largely means that the index will remain available for use during rebuild and my procs and query will be able to use it during rebuild. Also my understanding was that table will be locked very briefly while the schema change will be completing.But when I was rebuilding the clustered index online on a large table with some 3 million records, the table got locked and I was not able even to read the data from it for some 5 minutes. Then I cancelled the operation as it was production server and it was one of our main transaction table.
Is rebuilding index online supposed to work this way? The table has no other index.The parameteres I used are:
REBUILD WITH (PAD_INDEX = ON, SORT_IN_TEMPDB = ON, ONLINE = ON, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, FILLFACTOR = 95)
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Jun 18, 2015
I have created NONCLUSTERED index on table but my report is taking more time that's why i created columnstore NONCLUSTERED index on the same table but i have one query, if any table have row and column level index(same columns in index) . Which index query will consider.
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Aug 18, 2015
i have created a fact table which has unique cluster index as below,
CREATE UNIQUE CLUSTERED INDEX [FactSales_SalesID] ON [dbo].[FactSales] (salesid ASC)
WITH (DATA_COMPRESSION = PAGE)
GO
however later when i add CLUSTERED COLUMNSTORE INDEXES :
CREATE CLUSTERED COLUMNSTORE INDEX CSI_FactSales
ON dbo.FactSales WITH (DATA_COMPRESSION = COLUMNSTORE)
GO
it prompts error.
Msg 35372, Level 16, State 3, Line 167 You cannot create more than one clustered index on table 'dbo.FactSales'. Consider creating a new clustered index using 'with (drop_existing = on)' option.
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Jul 9, 2014
I understand that minimal logging can occur on a non clustered indexed heap as long as [URL] ...
*not replicated
*tablock is used
*table is empty
The following test seems to contradict this
In the test I create a non indexed heap, insert some record and check the log, then repeat the test on an indexed heap.
The results suggest that even though the conditions for minimal logging into a indexed heap are met, minimal logging is not happening although it does happen on an non indexed heap. What am I doing wrong?
CREATE DATABASE logtest
GO
USE logtest
GO
CREATE TABLE test (field varchar(100))
GO
CHECKPOINT
[Code] ....
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