Anyone can explain to me if the expression
SELECT ... WHERE Column IN (..., ...)
use the indexes or it's better to use the
SELECT ... WHERE Column = ... OR Column = ...
what is the best for the engine!?
Regards
Paulo Aboim Pinto
Odivelas - Portugal
Hi,Would like to know the performance differenece between Multi-columnIndex vs Single Column Indexes. Let's say I have a table with col1,col2, col3 along with a primary key column and non-indexed columns.In queries, I will use col1, col2, and col3 together and some timesjust one or two of these three columns. My questions is, should Icreate one index contains col1, col2, and col3, or create 3 seperatedcolumns. I.e. each column has its own index. Any performancedifference?Thanks a lot.
View 1 Replies View RelatedHi,
I'm try to get the total number of the indexes in a Sql CE database table. Is there a way to 'select count(*)' the indexes?
Cheers,
Justin
Is it possible to copy tables with SELECT INTO and let the created table have the same indexes as the original table copied from?
Thanks
Uwe
hi,
I have a dba with more than 500 tables and I want to drop the indexes on the least selective columns. How do I know which are the poor indexes?
Please help.........thanks
The largest table in the database is not referenced by any other table. Primary key is identity column. I know that I shouldn’t make clustered index on that column, but what if I don’t index that column at all? Will it be some negative consequences of that decision?
View 2 Replies View RelatedWe have two non cluster indexes on the same column for a table. let me know will it impact negatively on table like performance etc. ?
View 4 Replies View RelatedHi All
I have a table with indexes as follows
license_detail_prim
clustered, unique located on PRIMARY
component_id, license_id
LICENSE_DTL_IDX_LICENSE_ID
nonclustered located on PRIMARY
license_id
PK__license_dtl__6EB64F9B
nonclustered, unique, primary key located on PRIMARY
component_id, license_id
XIF39license_dtl
nonclustered located on PRIMARY
license_id
from the above, it is evident that multiple indexes have been created on the same columns
What is the side effects of havins such table design.
Thanks
Is there a way to compare tables in 2 different databases to find out if they have the same indexes and column names and keys. Or maybe a tool i dont know about.
View 1 Replies View RelatedI 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!
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.
View 3 Replies View RelatedI wanted to find all occurrences of ADRSCODE in a Database where ADRSCODE is in either an Index or a Primary Key.
I know how to get all of the occurences of ADRSCODE in a database and the table associated with it, I just want to tack on the Index and/or primary key.
SELECTOBJECT_NAME(object_id)FROMsys.columns
WHEREname
='foo'
How can I get the other bit of information ?
I had an existing table with lots of indexes.
As a test (fro speed) - I added a non clustered column-store index.
When I run test queries it always ignores my new column-store index. Why?
Should I remove the old indexes, leaving just the column store?
I hope i'm in the right place, but thanks anyway....
Actually i have 2 questions (regarding sql-server Indices/Keys):
1) I have an index, which is consisted of 4 columns.
I've read elsewhere that this index functions (as well) as an index (single column
index) on the first column of this multi-column index.
Does this mean that if i'd like to have (in addition) Indices on all of the 4 columns
seperately i need to define only 3???
2) I have a unique key consisted of multiple columns.
I'd like to save an index to this combination of columns as well (to speed up
things in DB...).
Does the definition of a multiple-columns key free me from defining the multiple-
columns index???
can anyone explain the main diference between Keys and Indices???
I have a database in which I have some tables in which I have implemented Clustered columnstore Index. How to find the fragmentation levels of all these indexes via a single T-SQl script
View 3 Replies View RelatedI hope i'm in the right place, but thanks anyway....
Actually i have 2 questions (regarding sql-server Indices/Keys):
1) I have an index, which is consisted of 4 columns.
I've read elsewhere that this index functions (as well) as an index (single column
index) on the first column of this multi-column index.
Does this mean that if i'd like to have (in addition) Indices on all of the 4 columns
seperately i need to define only 3???
2) I have a unique key consisted of multiple columns.
I'd like to save an index to this combination of columns as well (to speed up
things in DB...).
Does the definition of a multiple-columns key free me from defining the multiple-
columns index???
can anyone explain the main diference between Keys and Indices???
thanks,
Ran Kizi
Somewhere i read..that in SQL Server...usage of Built-in Functions on Columns, makes query optimizer to ignore indexes on that column...!
So lets say we have table EMP with Emp_id and Emp_Name....
Also we have Non-Clustered index on Emp_Name.
So following query would NOT use Non-Clustered index on Emp_Name column.
SELECTLEFT(emp_name, 3) as emp3
FROMdbo.EMP
Is this true? i am using SQL Server 2008.
I'm working to improve performance on a database I've inherited, and there are several thousand indexes. I've got a list of ones which should definitely exist within the database, and I'm looking to strip out all the others and start fresh, though this list is still quite large (1000 or so).
Is there a way I can remove all the indexes that are not in my list without too much trouble? I.e. without having to manually go through them all individually. The list is currently in a csv file.
I'm looking to either automate the removal of indexes not in the list, or possibly to generate the Create statements for the indexes on the list and simply remove all indexes and then run these statements.
As an aside, when trying to list all indexes in the database, I've found various scripts to do this, but found they all seem to produce differing results. What is the best script to list all indexes?
Example, suppose you have these 2 tables(NOTE: My example is totally different, but I'm simply trying to setupthe a simpler version, so excuse the bad design; not the point here)CarsSold {CarsSoldID int (primary key)MonthID intDealershipID intNumberCarsSold int}Dealership {DealershipID int, (primary key)SalesTax decimal}so you may have many delearships selling cars the same month, and youwanted a report to sum up totals of all dealerships per month.select cs.MonthID,sum(cs.NumberCarsSold) as 'TotalCarsSoldInMonth',sum(cs.NumberCarsSold) * d.SalesTax as 'TotalRevenue'from CarsSold csjoin Dealership d on d.DealershipID = cs.DealershipIDgroup by cs.MonthIDMy question is, is there a way to achieve something like this:select cs.MonthID,sum(cs.NumberCarsSold) as 'TotalCarsSoldInMonth',TotalCarsSoldInMonth * d.SalesTax as 'TotalRevenue'from CarsSold csjoin Dealership d on d.DealershipID = cs.DealershipIDgroup by cs.MonthIDNotice the only difference is the 3rd column in the select. Myparticular query is performing some crazy math and the only way I knowof how to get it to work is to copy and past the logic which isgetting out way out of hand...Thanks,Dave
View 5 Replies View RelatedUsing SQL Server 2000. How can I refer to one alias in another column?E.g., (this a contrived example but you get the idea)SELECT time, distance, (distance / time) AS speed, (speed / time) AS acceleration FROM dataNote how the speed alias is used in the definition of acceleration alias but this doesn't seem to work.
View 11 Replies View RelatedUsing SQL Server 2000. How can I refer to one alias in another column?
E.g., (this a contrived example but you get the idea)
SELECT time, distance, (distance / time) AS speed, (speed / time) AS acceleration FROM data
Note how the "speed" alias is used in the definition of "acceleration" alias but this doesn't work.
Hello All,Is there a way to run sql select statements with column numbers inplace of column names in SQLServer.Current SQL ==> select AddressId,Name,City from AddressIs this possible ==> select 1,2,5 from AddressThanks in Advance,-Sandeep
View 1 Replies View Relatedi need help to get the value of a column which is selected from a column of another table....
View 3 Replies View Relatedi dont't know how to select row with max column value group by another column. I have T-SQL
CREATE PROC GET_USER AS
BEGIN
SELECT T.USER_ID ,MAX(T.START_DATE) AS [Max First Start Date] ,
MAX(T.[Second Start Date]) AS [Max Second Start Date],
T.PC_GRADE,T.FULL_NAME,T.COST_CENTER,T.TYPE_PERSON_NAME,T.TRANSACTION_NAME,T.DEPARTMENT_NAME ,T.BU_NAME,T.BRANCH_NAME,T.POSITION_NAME
FROM (
[code]....
I am studying indexes and keys. I have a table that has a fixed width of data to be loaded in the first column which is parsed in a view based on data types within the fixed width specifications.
Example column A:
(name phone house cost of house,zipcodecountystatecountry)
-a view will later split this large varchar string basedÂ
column b: is the source filename of the data load (varchar 256)
....
a. would there be a benefit of adding a clustered or nonclustered index (if so which/point in direction on why)
b. is there benefit of making one of these two columns a primary key (millions of records) or for adding a 3rd new column as a pk?
c. view: this parses the data in column a so it ends up looking more like "name phone house cost of house zipcode county state country" each having their own column.
-any pros/cons of adding indexes (if so which) to the view instead of the tables or both for once the data is parsed?
I want to know how to select a Column without selecting a column name
View 6 Replies View RelatedFor example,I have a table "authors" with a column "author_name",and it has three value "Anne Ringer,Ann Dull,Johnson White".Here I want to create a new table by using a select sentence,its columns come from the values of the column "author_name".
can you tell me how can I complete this with the SQL?
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?
Not sure if this is possible, but maybe. I have a table that contains a bunch of logs.
I'm doing something like SELECT * FROM LOGS. The primary key in this table is LogID.
I have another table that contains error messages. Each LogID could have multiple error messages associated with it. To get the error messages.
When I perform my first select query listed above, I would like one of the columns to be populated with ALL the error messages for that particular LogID (SELECT * FROM ERRORS WHERE LogID = MyLogID).
Any thoughts as to how I could accomplish such a daring feat?
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] ....
What is the difference please?
View 1 Replies View RelatedIs there a way to select a column number without knowing its name? For example I want to select column 3 of a file without knowing it is:
Select [column 3] FROM OPENROWSET ('MSDASQL', 'Driver={Microsoft Text Driver (*.txt; *.csv)};
DefaultDir=D:ReportsTest;','select * from Report.txt ')
How do I get all the entries in a column, but make it so that there is only one occurance of each unique item.
View 4 Replies View Related