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Is it possible to create Cluster Index on Unique Key Column?

Posted By :Virendra Dugar     Posted Date :October 07, 2009    Points :10   Category :Sql Server 
Unique key column by default creates a non-cluster index on the column. Primary key creates cluster index on the column. The only difference is Unique key column allows only one null value. So is it possible to have cluster index on Unique key column?

The answer is YES. Though Unique key allows null value but it still maintains the uniqueness of the column.

You can also find related Interview Question to Is it possible to create Cluster Index on Unique Key Column?  below: 

What will you do if you need to create clustered index on more than one field? Is it possible?

The answer is yes and no.
You can create clustered index only one clustered index in table.
Either you can create index on entire table or you can create clustered index on a view covering entire table.
Suppose, you have created table with following:
CREATE TABLE [dbo].[Table1](
[field1] [int] IDENTITY(1,1) NOT NULL,
[field2] [nchar](10) ,
[field3] [nchar](10) ,
[field4] [nchar](10)
Create index on entire table:
CREATE INDEX idx_coverTable ON Table1(field1, field2) INCLUDE (field3, field4)
Create clustered index on a view covering entire table:
SELECT field1, field2, field3, field4 FROM dbo.Table1
CREATE UNIQUE CLUSTERED INDEX idx_viewClustered ON dbo.v1111(field1, field2, field3, field4)
GO (More...)

How to create a Unique Indix?

Create UNIQUE INDEX Index_Name

What is a table called, if it does not have neither Cluster nor Non-cluster Index? What is it used for?

Unindexed table or Heap. Microsoft Press Books and Book On Line (BOL) refers it as Heap.
A heap is a table that does not have a clustered index and, therefore, the pages are not linked by
pointers. The IAM pages are the only structures that link the pages in a table together.
Unindexed tables are good for fast storing of data. Many times it is better to drop all indexes from table and than do bulk of inserts and to restore those indexes after that. (More...)

Database: State Can an Identity column be index?

No, Identity and GUID column do not need to be indexed. (More...)

What is Private Constructor? and it's use? Can you create instance of a class which has Private Constructor?

When a class declares only private instance constructors, it is not possible for classes outside the program to derive from the class or to directly create instances of it. (Except Nested classes)
Make a constructor private if:

1) You want it to be available only to the class itself. For example, you might have a special constructor used only in the implementation of your class' Clone method.

2) You do not want instances of your component to be created. For example, you may have a class containing nothing but Shared utility functions, and no instance data. Creating instances of the class would waste memory. (More...)

What is a Index?

To execute the Quesry faster (More...)

What are the requirements to create a CLR based user-defined type?

CLR must be enabled for the instance and A class created with a CLR-compatible language. (More...)

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