Many times we see tables with customerID as the PK and clustered but with customerName as null.
So, I try to inforce it by alter table add constraint of AK1_customerName unique for it. However, though the uniqueness is enforced, the display sequence is also 'altered' to be sorted by customerName?
This does not look like right...
-D
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.
View 4 Replies View RelatedI 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]....
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?
Hello,
How do I restore a sql database that is on a clustered server from a sql database backup file that is on a non_clustered server?
Thanks,
Serey
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.
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
What is the easiest way to remember the definitions of clustered and non clustered indexes.
View 9 Replies View RelatedI have a really super slow stored proc that does something simple. it updates a table if certain values are received.
In looking at this the matching is done on the Primary Key, which is set as a Clustered index, looking further I have another constraint, that sets the same column to a Unique, Non-Clustered.
I am not sure why this was done, but it seems to be counter productive. I have read only references to Which one is better on a primary key, but not can their be both and if it is "Smart".
Hello,
I've a table with primary key defined as non-clusterd, now without dropping it can I modify the existing index to clustered through tsql as I had to write some migration script and in that script I wanna do this.
Thanks in Advance,
Rohit
I would like to find information on Clustered and Non-clustered indexes and how B-trees are used. I know a clustered index is placed into a b-tree which makes sense for fast ordered searching. What data structure does a non-clustered index use and how? I tried to find info. on the web but couldn't get much detail...
View 3 Replies View RelatedI 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>?
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?
So I'm reading http://www.sql-server-performance.com/tips/clustered_indexes_p2.aspx and I come across this:
When selecting a column to base your clustered index on, try to avoid columns that are frequently updated. Every time that a column used for a clustered index is modified, all of the non-clustered indexes must also be updated, creating additional overhead. [6.5, 7.0, 2000, 2005] Updated 3-5-2004
Does this mean if I have say a table called Item with a clustered index on a column in it called itemaddeddate, and several non-clustered indexes associated with that table, that if a record gets modified and it's itemaddeddate value changes, that ALL my indexes on that table will get rebuilt? Or is it referring to the table structure changing?
If so does this "pseudocode" example also cause this to occur:
sqlstring="select * from item where itemid=12345"
rs.open sqlstring, etc, etc, etc
rs.Fields("ItemName")="My New Item Name"
rs.Fields("ItemPrice")=1.00
rs.Update
Note I didn't explicitly change the value of rs.fields("ItemAddedDate")...does rs.Fields("ItemAddedDate")=rs.Fields("ItemAddedDate") occur implicitly, which would force the rebuild of all the non-clustered indexes?
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?
View 2 Replies View RelatedI 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] ....
Does creating both a Clustered and Non-Clustered on the same field increase performace or decrease performance?
Or having either one is enough?
What does an index add to the performance?
Why do we use Clustered Index and Non-clustered Index?
thanks
Dear All,
i've observed one particular table, one column is having clustered and non clustered index. is it ok? or i need to drop the non clustered column?
the table has 16 columns and at present 8 million records are there. per day approxmately 60000 rows will be getting into the table. it has another 3 non clustered indexes.
please suggest me.
Arnav
Even you learn 1%, Learn it with 100% confidence.
hi,
how clustered indexes and non-clustered indexes been saved in memory?
non-clustered is a table of a references to the actual table?
and what about clustered indexes?
thanks.
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
After applying SP3 to to cluster, cluster still displays that it has SP2, is there a way to check for sure which version it has. And what's the appropriate way to install SP3 on cluster.
View 1 Replies View Relatedwhere can i read more about this things, i can understand what this mean......
thanks
Well thank you for answering the last question
Also harsh, i dont know if you remeber me, but i hav got the job at mastek.
Ok now the next question is that.
What is better CLUSTERED or NON CLUSTERED index??.
please also comment on how efficient the combination of clustered and non clustered index works??
thank you
Trust in Technology mate .....'Not in Human Beings'
I've been doing a bit of reading and have read in quite a few placesthat an identity column is a good clustered index and that all or atleast most tables should have a clustered index. The tool I used togenerate tables made them all with non clustered indexes so I wouldlike to drop all of them and generate clustered indexes. So myquestions is a) good idea? and b) how? There are foreign key referencesto most of them so those would need to be dropped first and thenre-created after the clustered one was created and that could cascade(I think?)Any existing scripts out there that might do this? I found somethingsimilar and modified it, the sql is included below. This gives me thelist of all the columns I need, I just need to get the foreign keys foreach from here before each one and generate all the create/dropscripts.All the columns I am looking to do this for are called "Id" making thissomewhat simpler. I'm just looking to incrementally make the SQL sidebetter and don't want to rewrite a bunch of application level code tomake the column names ISO compliant, etc./*-- Returns whether the column is ASC or DESCCREATE FUNCTION dbo.GetIndexColumnOrder(@object_id INT,@index_id TINYINT,@column_id TINYINT)RETURNS NVARCHAR(5)ASBEGINDECLARE @r NVARCHAR(5)SELECT @r = CASE INDEXKEY_PROPERTY(@object_id,@index_id,@column_id,'IsDescending')WHEN 1 THEN N' DESC'ELSE N''ENDRETURN @rEND-- Returns the list of columns in the indexCREATE FUNCTION dbo.GetIndexColumns(@table_name SYSNAME,@object_id INT,@index_id TINYINT)RETURNS NVARCHAR(4000)ASBEGINDECLARE@colnames NVARCHAR(4000),@thisColID INT,@thisColName SYSNAMESET @colnames = INDEX_COL(@table_name, @index_id, 1)+ dbo.GetIndexColumnOrder(@object_id, @index_id, 1)SET @thisColID = 2SET @thisColName = INDEX_COL(@table_name, @index_id, @thisColID)+ dbo.GetIndexColumnOrder(@object_id, @index_id, @thisColID)WHILE (@thisColName IS NOT NULL)BEGINSET @thisColID = @thisColID + 1SET @colnames = @colnames + ', ' + @thisColNameSET @thisColName = INDEX_COL(@table_name, @index_id,@thisColID)+ dbo.GetIndexColumnOrder(@object_id, @index_id,@thisColID)ENDRETURN @colNamesENDCREATE VIEW dbo.vAllIndexesASbeginSELECTTABLE_NAME = OBJECT_NAME(i.id),INDEX_NAME = i.name,COLUMN_LIST = dbo.GetIndexColumns(OBJECT_NAME(i.id), i.id,i.indid),IS_CLUSTERED = INDEXPROPERTY(i.id, i.name, 'IsClustered'),IS_UNIQUE = INDEXPROPERTY(i.id, i.name, 'IsUnique'),FILE_GROUP = g.GroupNameFROMsysindexes iINNER JOINsysfilegroups gONi.groupid = g.groupidWHERE(i.indid BETWEEN 1 AND 254)-- leave out AUTO_STATISTICS:AND (i.Status & 64)=0-- leave out system tables:AND OBJECTPROPERTY(i.id, 'IsMsShipped') = 0end*/SELECTv.*FROMdbo.vAllIndexes vINNER JOININFORMATION_SCHEMA.TABLE_CONSTRAINTS TONT.CONSTRAINT_NAME = v.INDEX_NAMEAND T.TABLE_NAME = v.TABLE_NAMEAND T.CONSTRAINT_TYPE = 'PRIMARY KEY'AND v.COLUMN_LIST = 'Id'AND v.IS_CLUSTERED = 0ORDER BY v.TABLE_NAME
View 5 Replies View RelatedWe have two SQL servers, one in NY, one in Illinois, and we
want to sync them. Suppose we have a T1 line as backbone,
which one is a better solution for us, Clustered or SQL
replication ? Your help will be greatly appreciated!
Xiao
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.
Pleased help...If this question has enough wording or try at least.
Between a Clustered and a Nonclustered which one is faster or quicker? And if so, why is that?
Thank You.
Does anybody know if a key defined on Uniqueidentifier datatype is a good candidate for the clustered index or otherwise.
View 1 Replies View RelatedI have read the readme, but just want to be sure. When installing sp3 on a clustered server (1 primary node with 1 secondary node as failover), all you have to do is log into the server that currently has all the resources and run the sp3 setup?
Is there anything else to it? Anything to watch out for?
I only have one instance and there's no replication or analysis services or anything else.
Unfortunately, I don't have another clustered server to test it on (long story - working on it)
Thanks in advance.
Can anyone help ?
If you have a clustered index on an identity field are appends then forced onto the last page anyway because of the identity field order. So is there any advanbtage of having a clustered identity field ?
HELP!!!!!!!!!!!!!!!!!!
I loaded SQL SP5a last night on my SQL Server and now none of my users can connect and run their applications.
I removed the virtual server and loaded the sp without any problems (so it seemed). "sa" works fine.
I am getting login failed errors:
Sql State 28000 and Sql Server 4002
Any thougts, ideas, curses would be GREATLY APPRECIATED!!!!!!!!!!!!
I need to convert several tables that currently have nonclustered indexes (primary keys) to clustered. Could anyone suggest what the easiest way of doing this would be.
View 1 Replies View Related