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Questions tagged [clustered-index]

A clustered index determines the physical order of data in a table.

A clustered index determines the physical order of data in a table. As the clustered index dictates the physical storage order of the data in the table, a table can contain only one clustered index. However, the index can comprise multiple columns (a composite index), like the way a telephone directory is organized by last name and first name.

A clustered index is particularly efficient on columns that are often searched for ranges of values.

Source: MSDN (Using Clustered Indexes)

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What do Clustered and Non-Clustered index actually mean?

I have a limited exposure to DB and have only used DB as an application programmer. I want to know about Clustered and Non clustered indexes. I googled and what I found was : A clustered index is a special type of index that reorders the way …
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What are the differences between a clustered and a non-clustered index?

What are the differences between a clustered and a non-clustered index?
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Difference between clustered and nonclustered index

I need to add proper index to my tables and need some help. I'm confused and need to clarify a few points: Should I use index for non-int columns? Why/why not I've read a lot about clustered and non-clustered index yet I still can't decide when to…
Pabuc
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SQL Server - When to use Clustered vs non-Clustered Index?

I know primary differences between clustered and non clustered indexes and have an understanding of how they actually work. I understand how clustered and non-clustered indexes improve read performance. But one thing I am not sure is that what would…
armulator
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Do clustered indexes have to be unique?

What happens if a clustered index is not unique? Can it lead to bad performance because inserted rows flow to an "overflow" page of some sorts? Is it "made" unique and if so how? What is the best way to make it unique? I am asking because I am…
littlegreen
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About clustered index in postgres

I'm using psql to access a postgres database. When viewing the metadata of a table, is there any way to see whether an index of a table is a clustered index? I heard that the PRIMARY KEY of a table is automatically associated with a clustered index,…
twimo
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How can I tell if a database table is being accessed anymore? Want something like a "SELECT trigger"

I have a very large database with hundreds of tables, and after many, many product upgrades, I'm sure half of them aren't being used anymore. How can I tell if a table is is actively being selected from? I can't just use Profiler - not only do I…
SqlRyan
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How to change the primary key to be non-clustered?

Part-time reluctant DBA here. I want to change an existing primary key index from clustered to non-clustered. And the syntax is escaping me. This is how it's scripted out right now. ALTER TABLE [dbo].[Config] WITH NOCHECK ADD CONSTRAINT…
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database: primary key, Clustered or NonClustered

I am creating a database in SQL server 2008, CREATE TABLE Users ( U_Id INT NOT NULL FirstName VARCHAR(50) NOT NULL, LastName VARCHAR(50) NOT NULL, Email VARCHAR(200) Password VARCHAR(50) ) I want to make U_Id the primary key. I…
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Should I get rid of clustered indexes on Guid columns

I am working on a database that usually uses GUIDs as primary keys. By default SQL Server places a clustered index on primary key columns. I understand that this is a silly idea for GUID columns, and that non-clustered indexes are better. What do…
cbp
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SQL Server heap v.s. clustered index

I am using SQL Server 2008. I know if a table has no clustered index, then it is called heap, or else the storage model is called clustered index (B-Tree). I want to learn more about what exactly means heap storage, what it looks like and whether it…
George2
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How to reduce clustered index scan cost by using SQL query

How can I reduce the clustered index scan cost of below mentioned query DECLARE @PARAMVAL varchar(3) set @PARAMVAL = 'CTD' select * from MASTER_RECORD_TYPE where RECORD_TYPE_CODE=@PARAMVAL if I run the above query it was showing index scan 99 %…
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How to create a Clustered Index with Entity Framework Core

From EF6.1, we have a way of specifying a clustered index on a property public class Person { [Index(IsClustered = true, IsUnique = true)] public long UserName { get; set; } } But this Index attribute does not seem to be in EF Core right now?…
Ray
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SQL Server: Clustered index on datetime, ASC or DESC

If I have an SQL Server table with a clustered index on a datetime field, that is set to DateTime.Now (from C#) before inserts, should the index be ascending or descending to avoid reorganization of the table? Thanks.
Eyvind
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Performance of Non Clustered Indexes on Heaps vs Clustered Indexes

This 2007 White Paper compares the performance for individual select/insert/delete/update and range select statements on a table organized as a clustered index vs that on a table organized as a heap with a non clustered index on the same key columns…
Martin Smith
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