SQL Server 2008 :: Put Clustered Index On 8 Column Natural Key Or On Identity Key
Aug 2, 2015
I am extremely new to database design, and I ran into a problem that I know comes up often, however has many opinions...
Basically I have a table that is going to have 50+ columns. The natural key on this table is actually 8 columns wide, 4 of them being Varchar columns by default. (varchar(50)'s).
I have added an identity column, (1,1) to the table, however I put the clustered index on the 8 natural keys... My plan is to rebuild the clustered index once nightly when the system isn't in use (after 7 pm).
I know others would say it would be better to have the clustered key on the 1,1 column and then add indexes on the other 8 fields... However I don't quite understand why honestly...
Every single query against this table will use the 8 columns, and will NOT use the Identity column (1,1) because they are calls from other systems that do not know the Identity column....
Therefore if your database is set up for query speed, and every single query has to have a value for 8 columns to get a valid result, does it make sense to put a clustered index over the 8 columns?
If not why? Why is putting a clustered index on an identity column (that will literally never be used in a query) a better solution?
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Sep 8, 2006
Hi there, I have a table that has an IDENTITY column and it is the PK of this table. By default SQL Server creates a unique clustered index on the PK, but this isn't what I wanted. I want to make a regular unique index on the column so I can make a clustered index on a different column.
If I try to uncheck the Clustered index option in EM I get a dialog that says "Cannot convert a clustered index to a nonclustered index using the DROP_EXISTING option.". If I simply try to delete the index I get the following "An explicit DROP INDEX is not allowed on index 'index name'. It is being used for PRIMARY KEY constraint enforcement.
So do I have to drop the PK constraint now? How does that affect all the tables that have FK relationships to this table?
Thanks
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Feb 27, 2015
After reading some comments here I decided to look at tables to see if any had a clustered index that was a unique identifier. Yep. So if I have a table with a unique identifier as the primary key/clustered index and an identity column that is indexed, I would like to make the identity a clustered index (maybe even the primary key) and make the unique identifier a unique non-clustered index (not the primary key).
Does this sound reasonable?If I do this will I need to drop and recreate the other indexes? Or maybe just rebuild the other indexes?
Currently:
CREATE TABLE Payments (
IDX INT IDENTITY(1,1) NOT NULL,
GUID UNIQUEIDENTIFIER NOT NULL DEFAULT(NEWID()),
.....
-- many other columns
);
GO
ALTER TABLE [dbo].[PAYMENTS] ADD CONSTRAINT [PK_PAYMENTS_GID] PRIMARY KEY CLUSTERED ([GUID] ASC);
GO
CREATE NONCLUSTERED INDEX [IX_Payments_ID] ON [dbo].[PAYMENTS] ([IDX] ASC);
GO
Would like:
ALTER TABLE [dbo].[PAYMENTS] ADD CONSTRAINT [PK_PAYMENTS_IDX] PRIMARY KEY CLUSTERED (IDX ASC);
GO
CREATE UNIQUE NONCLUSTERED INDEX [IX_Payments_GUID] ON [dbo].[PAYMENTS] (GUID ASC);
GO
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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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Apr 22, 2015
What is the best way to forecastestimate space for non-clustered index on a table?
Example :
Table name : Test123
Row : 170000000
Reserved : 18000000 KB
Data : 70000000 KB
Index: 40000000 KB
Note: Test123 already has clustered index and 2 non clustered indexes.
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May 18, 2015
I would like to put a Clustered Index on a date column in a current heap, but one question/concern.This heap every month has thousands of rows deleted and even more added later. How much of an issue will this cause the Clustered Index as far as page splits? I was thinking Fill Factor of 70%.I would normally just test and still will on Dev box, but my Dev box is much smaller than production as far as power.
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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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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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Oct 9, 2015
I am trying to use an indexed view to allow for aggregations to be generated more quickly in my test data warehouse. The Fact Table I am creating the indexed view on is a partitioned clustered columnstore index.
I have created a view with the following code:
ALTER view dbo.FactView
with schemabinding
as
select local_date_key, meter_key, unit_key, read_type_key, sum(isnull(read_value,0)) as [s_read_value], sum(isnull(cost,0)) as [s_cost]
, sum(isnull(easy_target_value,0)) as [s_easy_target_value], sum(isnull(hard_target_value,0)) as [s_hard_target_value]
, sum(isnull(read_value,0)) as [a_read_value], sum(isnull(temperature,0)) as [a_temp], sum(isnull(co2,0)) as [s_co2]
, sum(isnull(easy_target_co2,0)) as [s_easy_target_co2]
, sum(isnull(hard_target_co2,0)) as [s_hard_target_co2], sum(isnull(temp1,0)) as [a_temp1], sum(isnull(temp2,0)) as [a_temp2]
, sum(isnull(volume,0)) as [s_volume], count_big(*) as [freq]
from dbo.FactConsumptionPart
group by local_date_key, read_type_key, meter_key, unit_key
I then created an index on the view as follows:
create unique clustered index IDX_FV on factview (local_date_key, read_type_key, meter_key, unit_key)
I then followed this up by running some large calculations that required use of the aggregation functionality on the main fact table, grouping by the clustered index columns and only returning averages and sums that are available in the view, but it still uses the underlying table to perform the aggregations, rather than the view I have created. Running an equivalent query on the view, then it takes 75% less time to query the indexed view directly, to using the fact table. I think the expected behaviour was that in SQL Server Enterprise or Developer edition (I am using developer edition), then the fact table should have used the indexed view. what I might be missing, for the query not to be using the indexed view?
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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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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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Apr 28, 2015
I have two tables having one row identifier column each of int datatype. Both these columns are part of the respective primary keys. Now as a part of my process, i'm inserting one small part of data from one table to another table. This was working fine but suddenly started getting error like
Violation of PRIMARY KEY constraint 'PK_TargetTable'. Cannot insert duplicate key in object 'DW.TargetTable'. The duplicate key value is (58544748).First I checked with DBCC CHECKIDENT with NORESEED and found that there is difference in the current identity value and current column value. I fixed it by running DBCC CHECKIDENT. But to my surprise again got the same issue. interesting thing is that the error comes after inserting 65466 records.
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Mar 11, 2015
I am using following queries in a stored procedure.This stored procedure is executed through a dot net application.
DECLARE @DEPTNBR BIGINT
SELECT @DEPTNBR = DEPTNBR
FROM DEPARTMENT_DETAILS WITH (UPDLOCK,READPAST)
WHERE STATUS= 1
UPDATE DEPARTMENT_DETAILS SET STATUS= 0 WHERE DEPTNBR = @DEPTNBR
SELECT DEPTNBR,DEPTNAME,DEPTLOC FROM DEPARTMENT_DETAILS WHERE DEPTNBR = @DEPTNBR
From my queries,I am providing a available department information.Each user needs to get unique available department information.But when more number of users using the application concurrently, multiple users getting same department information.How to solve my problem?I always wants to get unique department information even though multiple users using the application concurrently.
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Jan 25, 2007
Users can approach their userprofile on my site using: www.mysite.com/name=peterName is a unique value within my database (db type: nvarchar(50))Now, I have created a clustered index on the username column.However, IMHO its faster to create a clustered index on the (also unique) usercode column since that is of type int.BUT since a user can approach my site based on username I feel that I HAVE to live with this setback in performance....Is that true or is there a better way to solve this issue?
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Apr 16, 2015
Is it always the best practice to have the partition column also as the column for clustered index?
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Apr 3, 2002
I have a database where records are Inserted by an external process.
There is no updating or deleting of the data once inserted. The table in
question has a Clustered Index on the Machine_ID (integer) (data is from
manufacturing processes). Each record bears a start and end time. Most
queries involve the Machine, a time span (start time between to points in
time), the Downtime Cause, and the Running Mode.
I want to add an index on the Start Time, the Downtime Cause, and the
Runtime Mode.
My question is: should this new index also contain the Machine_id column
or does the existence of the Clustered Index already on that column negate
its need in the new index?
RC - Dedicated to only creating original mistakes!
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Dec 24, 2014
I have 5 million rows of table, and going to create Non Clustered Index for Datetime values column. Creating Non clustered Index on Datetime value column will affect performance or not.
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May 29, 2007
Want to check my thinking with you folks...
I have a table with a clustered composite index, consisting of 3 columns, which together form a unique key. For illustration, the columns are C1, C2 & C3.
Counts of distinct values for columns are C1 425, C2 300,000 & C3 4,000,000
C3 is effectively number of seconds since 01/01/1970.
The usage of the table is typically, insert a row, do something else, then update it.
Currently, the index columns are ordered C3,C1,C2. Fill factor of 90%.
My thinking is that this composite index is better ordered C1,C2,C3.
My reasoning is that having C3 as the leading column, biases all the inserts towards one side of the indexes underlying B-tree, causing page splits. Also, there'll be a bunch of "wasted" space across the tree, as the values going into C3 only ever get bigger (like an identity), so the space due to the fill factor in lower values never gets used.
Welcome your thoughts.
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Oct 22, 2014
I need to find out all the tables in database, which has FK columns and don’t have any Non-clustered index on them.
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Apr 3, 2015
I've been asked to look at using Clustered Columnstore indexes for one of my tables. The table contains about 5 million records with about 50 columns. The max field size is a NVarchar(MAX) with max field length currently of about 4k characters. It's only about a gigabyte's worth of data. The table is about 50% R/W operations. Currently, we have multiple indexes with no clustered index due to some performance issues that happened in the past. I've been attempting to determine if it's even really worth it to switch over. I feel that the table is still fairly small with minimal columns and don't believe there will be any noticeable improvement over traditional indexing.
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Nov 24, 2015
I created composite clustered index key based on Gender and Salary column
The Query executed Successfully and <g class="gr_ gr_135 gr-alert gr_tiny gr_spell undefined ContextualSpelling multiReplace" data-gr-id="135" id="135">i</g>
got composite index key id Gender(-), Salary I <g class="gr_ gr_310 gr-alert gr_gramm undefined Grammar only-ins replaceWithoutSep" data-gr-id="310" id="310">want</g> know why Gender(-) display like this?
And Gender is <g class="gr_ gr_391 gr-alert gr_spell undefined ContextualSpelling ins-del multiReplace" data-gr-id="391" id="391">nvarchar</g> (20)
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Sep 17, 2015
How can we get the list of clustered columnstore index in a database in sql server 2014
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Feb 18, 1999
I have an non-clustered index defined on an identity column(statusid) on a table containing 200k rows. The query optimizer chooses to do a table scan when doing the following select. Why would this be.
SELECT * FROM STATUS
WHERE statusid = 10000
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Sep 4, 2015
We are going to use SQL Sever change tracking. The problem is that some of our tables, which are to be tracked, have no primary keys. There are only unique clustered indexes. The question is what is the best way to turn on change tracking for these tables in our circumstances.
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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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Jun 19, 2008
Hi,
I am having problem in bulk update of a sql server table haning identity column from a datatable( has no identity column) using sqlbulkcopy. I tried several approaches, but it does not show any error nor is the table getting updated. But the identity value seems to getting increased every time.
thanks.
varun
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Jul 19, 2013
I have created two tables. table one has the following fields,
Id -> unique clustered index.
table two has the following fields,
Tid -> unique clustered index
Id -> foreign key of table one(id).
Now I have created primary key for the table one column 'id'. It's created as "nonclustered, unique, primary key located on PRIMARY". Primary key create clustered index default. since unique clustered index existed in table one, it has created "Nonclustered primary key".
My Question is, What is the difference between "clustered, unique, primary key" and "nonclustered, unique, primary key"? Is there any performance impact between these?
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Jun 26, 2015
In my database all columns have Identity Value as a PK.
Now today I check Index Fragmentation I saw that many cluster and Non cluster Index are avg.Fragmentation is around 99 % I thought that in Identity column record is always inserted at bottom so there is no fill factor assigned to it.
So in this case Do I need to set Fill factor for Cluster and Non Cluster Index?
If Yes Then For PK How much - 95 % or what? and same for Non cluster or It should around 85 to 90
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Mar 27, 2007
Hello,
I have a table with an Identity Column set up. I also have an index on the table that is set to Ignore Duplicate. Identity starts at 1 and is incremented by 1.
So first 5 rows inserted get identity
1
2
3
4
5
If I insert rows that get ignored because of the index with Ignore Duplicate, it is ignored correctly. But, the next row to get inserted will have an identity value of 7.
So, even though the insert was ignored because of the index with Ignore Duplicate, the Identity column was incremented behind the scenes.
Is there any way to avoid this?
Thanks,
John
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Feb 4, 2015
We have a table, which has one clustered index and one non clustered index(primary key). I want to drop the existing clustered index and make the primary key as clustered. Is there any easy way to do that. Will Drop_Existing support on this matter?
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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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Jun 25, 2015
I have a requirement to only rebuild the Clustered Indexes in the table ignoring the non clustered indexes as those are taken care of by the Clustered indexes.
In order to do that, I have taken the records based on the fragmentation %.
But unable to come up with a logic to only consider rebuilding the clustered indexes in the table.
create table #fragmentation
(
FragIndexId BigInt Identity(1,1),
--IDENTITY(int, 1, 1) AS FragIndexId,
DBNAME nvarchar(4000),
TableName nvarchar(4000),
[Code] ....
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Dec 1, 2014
I have a query which is primarily a victim of blocking and a blocker itself for other queries. I studied the plan for this and it shows a 42% cost on CI insert operation. The insert is happening on a table (Table A) that has a PK. This PK is not a running number. It is also a business key (primary key) in another master table (Table B).
My understanding is that the cost is heavy because -
1, this PK is not an incremental number. It could be any number not in a sequence.
2. while inserting into CI, there must be a scan happening to find out the location where the index will be inserted.
How can I reduce the cost?
1. Should I go for partitioning of this table Table A? I am trying to do this but I am not able to find any suitable partition key looking at the JOINS and filter clauses where this table is being used in the applicaiton.
2. Should I introduce a surrogate key (running number) as a primary key so that CI is faster ?
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