please 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
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 have a really strange problem.
I execute this query:
declare @cid int
set @cid = 2003227
select * from sales s, product p where p.product_Id = s.product_Id and customer_id = @cid
select * from sales s, product p where p.product_Id = s.product_Id and customer_id = @cid or @cid = 0
3 Million rows in sales, 120000 in product.
The first does and index seek, the second an index scan.
The execution plan reports that the scan takes 99.87% of the cost, and the seek takes 0.13%
This problem obviously gets worse the bigger the dataset / query /etc.
The reason I query this, is because it never used to take this long to do index scans. Is there something i can change, something i can fix?
Any help would be appreciated.
Josh
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 have created a nolock view off a table to prevent locks. I have users coming in through MS Access that have switched their queries to run against the views. Now we are noticing that queries that used to run as a clustered index seek against the table are running as a clustered index scan against the table and performance in the queries has dropped.
Is there any way that the same query that hits the view instead of the table can be made to run faster or at least use the index seek?
Thanks,
Steve
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?
If you display the execution plan and run the following:SET STATISTICS IO ONgoSELECT ProductID, SupplierIDFROM ProductsWHERE SupplierID = 1I don't understand how come there is noBookmark Lookup operation happening to get theProductID?I only see an Index Seek happening on SupplierID.There is no composite index SupplierID + ProductIDso what am I not understanding here?Thank you
View 3 Replies View RelatedHi,
Can I use index seek and still keep 'like' 'or' functionality for the following statement?
--prepare test table
create table entity (Id int identity(1,1), FamName varchar(200), LastName varchar(200))
go
create clustered index entity_id on entity (id)
go
create nonclustered index entity_lastName on entity (lastName)
go
insert into entity select famName,FirstName from table
--test index
declare @LastName varchar(10)
set @LastName = 'a'
select FamName
from entity
where @LastName is null or LastName like @LastName --clustered index scan
create table t1(a varchar(50) , b varchar(50))
create index i1 on t1(a)
create index i2 on t1(b)
create view v1
as
select * from t1 where isnull(a,b) = 'test'
select * from v1
The above SQL "select * from v1" is doing a table scan.
What do I do to make it perform an index seek ????
TIA
- ForXLDB
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 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 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,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%'
View 1 Replies View RelatedI 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 '
I am using Full Text Index to index emails stored in BLOB column in a table. Index process parses stored emails, and, if there is one or more files attached to the email these documents get indexed too. In result when I'm querying the full text index for a word or phrase I am getting reference to the email containing the word of phrase if interest if the word was used in the email body OR if it was used in any document attached to the email.
How to distinguish in a Full Text query that the result came from an embedded document rather than from "main" document? Or if that's not possible how to disable indexing of embedded documents?
My goal is either to give a user an option if he or she wants to search emails (email bodies only) OR emails AND documents attached to them, or at least clearly indicate in the returned result the real source where the word or phrase has been found.
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
My SSIS package is running very slow taking so much time to execute, One task is taking 2hr for inserting 100k records, i have disabled unused index still it is taking time.I am rebuilding/Refreshing indexes and stats once in month if i try to execute on daily basis will it improve my SSIS Package performance?
View 2 Replies View RelatedKeep getting this error when positioning to the last page of a report.
Using Server 2003...SqlRpt Svcs 2000 sp2
Detail error msg:
Exception of type Microsoft.ReportingServices.ReportRendering.ReportRenderingException was thrown. (rrRenderingError) Get Online Help
Exception of type Microsoft.ReportingServices.ReportRendering.ReportRenderingException was thrown.
Index was out of range. Must be non-negative and less than the size of the collection. Parameter name: index
Anyone have any suggestions? Any way to find out what collection is blowing?...or where parameter name: index comes from?
hello friends
i have table1 and 200 coulumn of table1 :) i have 647.600 records. i entered my records to table1 with for step to code lines in one day :)
i select category1 category2 and category3 with select code but i have just one index.. it is productnumber and it is primarykey..So my select code lines is so slow.. it is 7-9 second.. how can i select in 0.1 second ? Should i create index for category1 and category2 and category3 ? But i dont know create index.. My select code lines is below.. Could you learn me and show me index for it ?? or Could you learn me and show me fast Select code lines and index or etc ??? Also my search code line have a dangerous releated to attaching table1 with hackers :)
cheersi send 3 value of treview1 node and childnode and child.childnode to below page.aspx :)
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
If Not Me.IsPostBack Then
If Request("TextBox1") IsNot Nothing ThenTextBox1.Text = Request("TextBox1")
End If
If Request("TextBox2") IsNot Nothing ThenTextBox2.Text = Request("TextBox2")
End If
If Request("TextBox3") IsNot Nothing ThenTextBox3.Text = Request("TextBox3")
End If
End If
Dim searchword As String
If Request("TextBox3") = "" And Request("TextBox2") = "" Then
searchword = "Select * from urunlistesi where kategori= '" & Request("TextBox1") & "'"
End If
If Request("TextBox3") = "" Then
searchword = "Select * from urunlistesi where kategori= '" & Request("TextBox1") & "' and kategori1= '" & Request("TextBox2") & "'"
End If
If Request("TextBox3") <> "" And Request("TextBox2") <> "" And Request("TextBox1") <> "" Then
searchword = "Select * from urunlistesi where kategori= '" & Request("TextBox1") & "' and kategori1= '" & Request("TextBox2") & "' and kategori2= '" & Request("TextBox3") & "'"
End If
SqlDataSource1.SelectCommand = searchword
End Sub
Hi,
I'm running a merge replication on a sql2k machine to 6 sql2k subscribers.
Since a few day's only one of the merge agents fail's with the following error:
The merge process could not retrieve generation information at the 'Subscriber'.
The index entry for row ID was not found in index ID 3, of table 357576312, in database 'PBB006'.
All DBCC CHECKDB command's return 0 errors :confused:
I'm not sure if the table that's referred to in the message is on the distribution side or the subscribers side? A select * from sysobjects where id=357576312 gives different results on both sides . .
Any ideas as to what is causing this error?
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 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?
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
Hi All,
I 'm working to improve some sql performance.
One of the major syntax inside the SELECT statment is ..
WHERE FIELDA IN (SELECT PARAVALUE FROM PARATABLE WHERE SESSIONID = "XXXXX" AND PARATYPE='A') AND
WHERE FIELDB IN (SELECT PARAVALUE FROM PARATABLE WHERE SESSIONID = "XXXXX" AND PARATYPE='B') AND
WHERE FIELDC IN (SELECT PARAVALUE FROM PARATABLE WHERE SESSIONID = "XXXXX" AND PARATYPE='C') AND
WHERE FIELDD IN (SELECT PARAVALUE FROM PARATABLE WHERE SESSIONID = "XXXXX" AND PARATYPE='D') AND
WHERE FIELDE IN (SELECT PARAVALUE FROM PARATABLE WHERE SESSIONID = "XXXXX" AND PARATYPE='E') AND
WHERE FIELDF IN (SELECT PARAVALUE FROM PARATABLE WHERE SESSIONID = "XXXXX" AND PARATYPE='F')
(It's to compare the field content with some user input parameter inside a parameter table... )
I think properly is that the SELECT ... IN is causing much slowness in the sql statement. I have indexed FIELDA , FIELDB, FILEDC etc and those PARAVALUE and PARATYPE in the PARATABLE table. But perfromance is still slow and execution takes >20 seconds for 200000 rows of records.
Do any one know if still any chance to improvide the performance like this?
Much Thanks,
Andy
I'm trying to find whether there is a dmv or system view that can help me see the last time an index was rebuilt or created. Assuming I rebuilt an index using tsql commands (not a job with a history), is there a way to find out the last time that index was rebuilt?
Thanks much.
Hi!
It's been always said that it is best to put index on commonly joined fields in the table. But putting too much index on the table would cause the table to be slow on insert and update.
My question is, how do you deal with your fields that uses look up tables? Like for example for these fields
- CountryID(smallint)
- CreatedBy(int)
- ModifiedBy(int)
- Status(tinyint)
Those fields don't come a big part in the table, though when I query the table I always join them with their respective primary table to get their respective text value. Do I still need to put Index & FK relationships to these fields?
What fields are normally good candidates for index or fk relationships?
Thanks,
Enzo
Can anybody tell me when the index table is created? I have a Ole DB Command transformation that deletes rows from a table, and the pipeline continues on to a fuzzy lookup. The fuzzy lookup is returning matches to some of the rows which were delted in the aformentioned Ole DB Command. If the index table is created during pre-execute, this would make some sense to me since those rows which get deleted still exist before the pipeline reaches the Ole DB Command transformation which deletes those rows. If this is the case, is there a way to delay the index table creation? If this is not the case, has anybody else ran into anything like this...is there some solution? Thanks for any help.
What is the difference between the Index and the Primary Key?
View 14 Replies View RelatedHi,
I just want to know whether any advantage or disadvantage
in doing Reorganize Index And Rebuild Index ....
Plz do comment on this ASAP !!!!
Thanks in advance
Regards
Arv
Hi,
I just want to know whether any advantage or disadvantage
in doing Reorganize Index And Rebuild Index ....
Plz do comment on this ASAP !!!!
Thanks in advance
Regards
Arv
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
Greetings
My Fuzzy Lookup task works beautifully when it generates the lookup index every time it runs, but as I'm planning on running this hundreds of times I'd like it to maintain the index via the trigger. However when it attempts to install the trigger via sp_FuzzyLookupTableMaintenanceInstall I get:
Description: "A .NET Framework error occurred during execution of user-defined routine or aggregate "sp_FuzzyLookupTableMaintenanceInstall":
System.Data.SqlClient.SqlException:
Error number 8101 is invalid.
(I've not included the full stack trace as I figured this would be enough)
The table currently has an After Insert and After Update trigger. CLR integration is enabled in this database instance. Is there some other option I need to set somewhere?
Thanks!!