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 '
How can I improve performance of my search if I am looking in a table with more than ten million rows with a "like query"?
Does putting an index mean only telling the computer to start in a particular order?
if I index all the coloums does my search get faster ?
how can I decide on an indexing strategy?
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?
I am running a SELECT on a table. This READ operation ends up going through Clustered Index Scan. I want to know whether Clustered Index Scan , blocks other concurrent transactions trying to INSERT into this table? Does Clustered Index Scan locks the entire clustered index?
View 3 Replies View RelatedI am trying to tune a process that is running slowly. I analyzed the process using the Database Engine Tuning Advisor, and it recommended the creation of 3 indexes, all non-clustered:
1) ColA, include ColB
2) ColA, include ColC
3) ColA, include ColD
So... I created a single non-clustered index on:
4) ColA, include ColB, ColC, ColD
That should do the same thing, right? A look at my execution plan shows that the index I created is being scanned -- 3 times. What is puzzling me, though, is that the Database Engine Tuning Advisor is still recommending I create these 3 separate indexes, even with the index (4) that I created in existence.
If it matters, ColA, ColB, ColC and ColD are all int FKs.
Hey,
what is the difference between Table Scan und Index Scan?
I find no difitions in the internet
Finchen
Hi,
I want to know wht is a
TABLE SCAN
INDEX SCAN
INDEX SEEKand When they are used, Wht is the difference between all these.????
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
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)
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.
View 1 Replies View RelatedI 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] ....
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>?
Hi, all experts here,
Thanks a lot for your kind attention.
As I am creating the non-clustered indexes for the tables, I dont quite understand how dose it really matter to put the columns in the index key columns or put them into the included columns of the index?
I am really confused about that and I am looking forward to hearing from you and thank you very much again for your advices and help.
With best regards,
Yours sincerely,
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]....
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 I'm issuing a SELECT on a field with the SUM on SQL Server 7. I have an index on the field in the WHERE clause but upon analysis, the Query Optimizer always uses a Full Table Scan. Can anyone explain why and is there a way to use the index.
HEre's the structure:
SELECT SUM(colA)
FROM TABLE tblB
GROUP BY colC
An index exists on column colC.
Thanks
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?
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
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
I want to know more details about the Clustered Index Delete. Is that Clustered Index Delete in the execution plan is good or bad or we can neglect that cost. Is there any way to avoid that clustered Index delete operator from the execution plan.
View 4 Replies View Related- What are your thoughts on adding clustered index on datetime (createdDate , native GUID) column. The data will be be physically organized in the clustered index allowing range operations to perform its duties. But will the GUID column make any impact ( drawbacks) should it be made part of the clustered key ?
The GUID column will provide the lookup with the required indexes to support.
I created a NC index as suggested by missing index DMV(of course I don't create them blindly). This one seemed to be a useful index but I now see from index usage stats that it only got scanned 50 times in 4 days.No seeks, no lookups. So is it a good idea keeping such index.The table on which this index is created is used more for reads and less for writes.
View 6 Replies View RelatedIs it always the best practice to have the partition column also as the column for clustered index?
View 2 Replies View Relatedplease explain the differences btween this logical & phisicall operations that we can see therir graphical icons in execution plan tab in Management Studio
thank you in advance
I would like to know the impacts (if any) of adding nonclustered index with included columns on large tables (these tables are populated by bulk insert from text files).
View 3 Replies View Relatedhow to reduce the cost of clustered index insert ?
View 8 Replies View RelatedI 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 ?
I have a table that has a clustered index that is only the identity column on the table. The table is somewhere around 200K rows and has 3800 pages in the index. We run our index maintenance every other day on this database using Ola's scripts and this index is rebuilt because it is 40-60% fragmented after 2 days. Overall, this isn't really too much of a problem since the index rebuild doesn't take too long, but I am puzzled as to how this index is getting fragmented since the only column in it is the identity.
CREATE TABLE [dbo].[Example](
[ExampleID] [int] IDENTITY(1,1) NOT NULL,
[ExampleCode] [varchar](10) NOT NULL,
[ForeignID] [int] NOT NULL,
[AnotherID] [int] NOT NULL,
[code]...
) ON [PRIMARY]There is nothing strange like updates to the identity happening and while some records are deleted, there has only been about 20,000 in the life of the table (months). Not enough to account for the level of fragmentation that we're seeing on the index.About the only thing I can think of that would cause fragmentation on this index in this scenario are:
1. Page splits caused by starting with a small value in one of the VARCHARs and later inserting a larger value
2. Page splits caused by the NULLABLE column, ExampleDate, starting with NULLs and later updating them to a date.
For #1, I had development check the update scenarios for the varchar columns, especially the varchar(1000) one, and they didn't see it as a common thing where the values would go from small (or empty) to large.
For #2, I checked and found that the only value for that column in the table is NULL so while it always starts as NULL, it never gets updated to anything else.
I've tried looking at sys.dm_db_index_operational_stats and the leaf_update_count is around 300,000, but unless those updates are causing page splits, I don't see how they would contribute to fragmentation.
I have a clustered index which shows as having a fragmentation level of 66% according to sys.dm_db_index_ physical_ stats.avg_ fragmentation_ in_ percent.
But no matter what I try the fragmentation level doesn't budge. And yes I'm updating the statistics after each attempt.Its not a huge issue the table only has 348 records. I'm testing a fixing fragmentation maintenance script. In Ironing out the syntax of my script I've fixed the fragmentation of indexes of over 65 % anyway..I've come across and index that I can't defragment. I've tried
ALTER INDEX ALL ON [GRIDINFO] REBUILD WITH (FILLFACTOR = 90)
I've tried
ALTER INDEX ALL ON [GRIDINFO] REORGANIZE
I've tried
DBCC INDEXDEFRAG (MYDATABASE, 'GRIDINFO', PK__GRIDINFO__3214EC2721F5FC7F);
The command complete successfully yet the avg_fragmentation_in_percent doesn't change. The table also has a nonclustered index. I've gleaned through all the statements of 'this will have no effect if' but so far I've not spotted a reason why this index won't defrag.The script has been modified to remove schema and database names for the forum.
dbcc showcontig('GRIDINFO','IDX_GRIDINFO1') with tableresults , all_levels
go
DBCC SHOWCONTIG ('GRIDINFO')
go
sp_helpindex 'GRIDINFO'
[code]....
I have Enterprise version of SQL Server 2012 & SQL server 2008. I understand that Image/Text/NText is obsoleted and should not be used. That being said I dont understand why I couldnt rebuild the following clustered index, while I could with nonclustered index, this happens on both SQL 2008 and 2012. Here are the DDL.
CREATE TABLE [dbo].[Demo](
[ID] [int] NOT NULL,
[FK_ID] [uniqueidentifier] NOT NULL,
[SomeColumn] [nvarchar](100) NOT NULL,
[Image] [image] NULL
) ON [PRIMARY] TEXTIMAGE_ON [PRIMARY]
[code]...
An online operation cannot be performed for index 'IX1_Demo' because the index contains column 'Image' of data type text, ntext, image or FILESTREAM. For a non-clustered index, the column could be an include column of the index. For a clustered index, the column could be any column of the table. If DROP_EXISTING is used, the column could be part of a new or old index. The operation must be performed offline.
--Online rebuild works fine on non clustered index
ALTER INDEX IX2_Demo ON Demo REBUILD WITH(ONLINE = ON)--It seems to me that some how having the Image datatype column in the table is an issue. eventhough that column is not part of the index.
I have a view that joins a dozen tables with a million rows added per year by an application. I want to materialize it. The view is always filtered by date first on reports, then there are a few key transaction keys, but then many other fields required to make each row unique. I don't want to add these columns since they are large, many, not used for sorting or filtering, and may not define uniqueness in a future application design. I need a uniqueifier that is application agnostic. I prefer a bigint. So to store the materialized view ideally for reporting, I want to add the following clustered index to materialize the view:
CREATE unique CLUSTERED INDEX idx1
ON [dbo].[myview](myDate, key1, key2, key3, id bigint identity(1,1) NOT NULL)
And I get this error:
Msg 102, Level 15, State 1, Line 3
Incorrect syntax near 'bigint'.
Can I do what I want? If so, how?
I am doing sp tuning. It has several lines. SO I divided into several small queries and executed individually and check the execution plans. In one small query, I found table scan is happening. That query is basically retrieving all columns from a table but the table doesn't have any pk or Indexes. So is it better to create non-clustered index to remove table sca.
View 2 Replies View RelatedI 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.