SQL 2005: Query Is Not Using Non-clustered Index! Need To Avoid Hints!
Oct 26, 2006
Greetings,
I have two tables:
CustomerOrder
----
ID
CustomerID
StatusID
CustomerOrderDetail
----
ID
Order_ID
StockID
Quantity
CustomerOrderDetail table has clustered unique index for ID and non-clustered for Order_ID
SQL Server 2005 is using table scan for CustomerOrderDetail table When I user the following query:
select
cod.*
from CustomerOrder co
inner join CustomerOrderDetail cod ON cod.Order_ID = co.ID
where
co.StatusID = 8 -- Pending
Both of the tables are pretty big, detail table has more than million records, so scanning the table is a bad idea.
When I specify hint to use index then sql seeks, but how do I make SQL server to use index automatically? I don't want to use hints in my queries.
Thanks!
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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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Apr 2, 2007
I would like to have some clarification about index-related recommendation from Database Tuning Advisor.
Let me describe the scenario first:
There is a table with clustered index defined on ID column of type INT and there are other columns of varchar/int types as well. Now when I run tuning advisor I get recommendations related to creating statistics as well as non-clustered indexes. When I view the syntax for recommended non-clustered index, sometime it explicitly add ID column as well which already has clustered index defined on it. e.g
CREATE NONCLUSTERED INDEX idx_TableName_IndexName ON dbo.TableName
(
ColName1 ASC,
ColName2 ASC,
ID ASC
)
My understanding is that for each non-clustered index, clustered index is automatically a part of it and that is how non-clustered index retrieve the actual data. I have seen it more often than not in DTA's recommendation to include clustered index column somewhere among columns for indexing for so many of my tables.
I can understand if the recommendation was to INCLUDE clustered-index column.
I would appreciate if someone out there could help me to understand what I am missing here.
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May 15, 2001
I am running SQL7 SP2 and and noticing table the query processor table scans when I ussue a between 'date1' and 'date2' instead of using the datetime index. If I put in the index hint (index = ix_datetimeXXXX) the query runs fine. My question is does this index hint restict the use of other indexes in the query and secondly how can I specify multiple index hints? Thanks in advance.
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Jul 23, 2001
Hello.
There is a trace flag that tells SQL Server to ignore index hinting in incoming queries. I'm having a Monday morning problem and I can't remember the trace number nor find it in my notes. Can anyone else come up with it?
Thanks in advance,
-darin
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Jul 27, 2015
I had some SQL queries which are using department ID for join , filter , Group By and Select so , i am having index on department ID of my table File Master scheme ..
CREATE TABLE [dbo].[FILE_MASTER](
[FILE_ID] [INT] IDENTITY(1,1) NOT NULL,
[DEPARTMENT_ID] [INT] NULL,
[CLIENT_ID] [INT] NULL
,[LEAD_DETAIL_ID] [INT] NULL
[code]....
The above index only working when there is condition or group by on department ID .and i when i am querying ..
SELECT DISTINCT CL.CLIENT_ID,CL.LOAN_SANCTION_DATE,MIN(CL.INWARD_DATE)AS Inward
FROM dbo.FILE_MASTER AS CL
GROUP BY CL.CLIENT_ID,CL.LOAN_SANCTION_DATE
and the plan is showing Index scan on index Indx_FM_department_ID .. Why it is not using Index seek , i guess i have both group by Columns in cover index included columns what is the use of cover index then ?
because if i am giving where condition before group by for specific Client ID , Loan Sanction Date it is telling to create separate index on client ID , Loan Sanction Date as per Execution Plan missing index detail ..
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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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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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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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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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Jun 3, 2006
Here is an extract from the Acc2Sql2.doc >>
By default, the Upsizing Wizard
transfers all indexes as nonclustered indexes. You can modify the Upsizing
Wizard to transfer the primary key index to a clustered index. To make this
change, start Microsoft Access and open the upsizing wizard library database.
For Microsoft Access 95, the filename is Wzcs.mda. For Microsoft Access 97, the
filename is Wzcs97.mda. When the database is open, click the Modules tab and open the
UT_ModUserConstants module. Search down to the UT_CLUSTERED constant. Change
the default value from False to True.
<<< end quote
Question: I am using ACCESS 2002 upsize wizard, I searched my computer for *.mda and could not find any wzcs*.mda. How do I set it so that it creates clustered-index instead of non-clustered-index?
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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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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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Nov 1, 2007
I have a table<table1> with 804668 records primary on table1(col1,col2,col3,col4)
Have created non-clustered index on <table1>(col2,col3,col4),to solve a performance issue.(which is a join involving another table with 1.2 million records).Seems to be working great.
I want to know whether this will slow down,insert and update on the <table1>?
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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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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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Sep 12, 2005
My experience with query hints are that they are just that, a hint. What I don't understand is when does SQL decide to ignore your hint?
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Sep 29, 2003
Please advise.
Whilst running a query I recieved the error below.
Cannot create a worktable row larger than allowable maximum. Resubmit your query with the ROBUST PLAN hint.
What is ROBUST PLAN hint?.
Help Appreciated.
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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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Sep 29, 2006
I have following query to delete the data from fact history table based on fact table. logid, level and post_date uniquely identify the rows on both fact and history table. I want to create indexes on the joined columns.I tried with clustered index (logid, level and post_date) it gives clustered index scan. I also tried with non clustered indexes on each column (logid, level and post_date) but still getting table scan.
Do you have any suggestion on which columns should I create proper indexes to avoid table or index scan? There are about 6 million rows on each table.
DELETE xbar_fact_history
FROM xbar_fact_history AS a
INNER JOIN xbar_fact AS b
ON a.logid = b.logid
AND a.level = b.level
AND a.post_date = b.post_date
AND a.check_CheckSum <> BINARY_CHECKSUM(b.out_mins,b.nor_hrs,b.pdi_call)
______________________________________________________________
Thanks
Sanjeev
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Jul 23, 2005
Hi,Here's my problem: I want to write a stored procedure that returns allrecords from a table that have a certain column starting with giventext. I however find that using LIKE and a variable always causes anindex scan... which is causing performance issues. My table has about3.5M records.Below is a test. In query analyser if I look at the execution plan forthe following it will come up as in index scan. However, if i justhard-code the text it all works fine (index seek).How can I do this with reasonable speed???Thanks GregDECLARE @find varchar(50)SET @find = 'start'SELECT TOP 100*FROM TestWHERECol1 LIKE @find + '%'--Col1 LIKE 'start%'
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Dec 6, 2005
What does an index add to the performance?
Why do we use Clustered Index and Non-clustered Index?
thanks
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Aug 23, 2007
I am trying to use hints and they don't seem to be working.
Something like:
select * from TABLE_NAME with (tablock,xlock)
fails.
Documentation clearly states that this is supported (TABLOCK, NOLOCK, XLOCK, etc.), so I must be missing something simple.
Please let me know how do I use Hints in SQL Server 2005 Compact.
Thanks.
PS.
I am using C#. It doesn't work in my code when I use
SqlCeDataReader rs = cmd.ExecuteReader();
And it doesn't work from inside the VS 2005 "query tool" or whatever it is called, when you do "Connect to Database" and so on.
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Dec 3, 2007
Do you know of a way, in the OLE DB Command (Executing a sql command for each record), to specify a lock hint?
Example: in my component, I want to update a table but I want to specify a ROWLOCK or UPDLOCK hint.
When I try using this sql statement in the 'SqlCommand' property:
UPDATE DIM_Accounts WITH (UPDLOCK)
SET COL1 = ''
SSIS gives a syntax error.
Do you know any workarounds?
Thanks!
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May 22, 2000
Hi,
I have a small table (around 10,000 rows) that is constantly selected from, deleted from, and inserted into. Basically we fill it with content, our web application selects the content, and when we run out, we regenerate (about 50 rows at a time). We currently have a nonclustered PK on the first two columns, both INTs. How can I determine if a clustered index would be better? I am concerned about bottlenecks due to a hotspot with the nonclustered index. When our site really starts to get users, this could become a big issue. I am thinking that I could use a clustered index, and set up a job to reindex the table once every hour or so....any help is appreciated greatly.
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Dec 9, 2000
Does anybody know if a key defined on Uniqueidentifier datatype is a good candidate for the clustered index or otherwise.
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Jun 29, 2007
Hi,
Is it advisable to create a Non Clustered Index in "ALLow NULL" column?
Thanks,
Rahul Jha
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Nov 11, 2012
In Microsoft SQL Management Studio 2005 I have the ability to add a single non clustered index on a table on multiple columns (ordered how I want) AND/OR I may create a multiple of these non-clustered Index entries with a single column per non-clustered index.
Is there a difference between to two options? If yes, how do these options work differently? I assume option 1 is just a faster way of creating the non-clustered index and there is no architectural difference!?
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Apr 13, 2008
Why can we have only one clustered index per table
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Oct 20, 2014
what is clustered index A and B.
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Jan 14, 2007
Hi,
I have a table which I would like to index.
The table holds info of nurses:
T_NURSE=(NurseCode, LName, FName, IDNumber ...)
NurseCode => PK+Identity
Since queries will be on LName (and optionally on FName and IDNumber) I created a clustered index with this order: {LName, FName, IDNumber, NurseCode}
Questions:
1.Is it ok to have the clustered index not the PK?
2.If yes - what importance does the PK have here?
Looking for a nurse via screen (using:LName,FName,ID) or via source-code (using:NurseCode) is 50%/50%.
Which field(s) should have the honor of being a PK?
3.If I perform the search using a view (SELECT * FROM vw_Nurse) will it use the index?
Thanks,
Izik
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