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What is the difference between a clustered and a non-clustered index?

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Question ajoutée par Utilisateur supprimé
Date de publication: 2016/04/05

Clustered Index

  • Only one per table
  • Faster to read than non clustered as data is physically stored in index order

Non Clustered Index

  • Can be used many times per table
  • Quicker for insert and update operations than a clustered index

Sikandar Amla
par Sikandar Amla , System Architect , Freelancer

The leaf nodes of a clustered index contain the data pages. A non-clustered index is a special type of index in which the logical order of the index does not match the physical stored order of the rows on disk. The leaf node of a non-clustered index does not consist of the data pages.

Clustered Index is a special type of index that reorders the way records in the table are physically stored.Therefore can only have one clustered index.

Non-clustered index in which the logical order of the index does not match the physical stored order of the row in the disk.

Smitha Rajan
par Smitha Rajan , Software Developer , Emirates India International Exchange

A clustered index determines the physical order of data in a table for this Reason a table can have only one clustered index.Primary key constraint creates clustered indexes automatically if no clustered index exists on the table.

 

A non-clustered index is analogues to an index in a text book. The data is stored in one place, the index in another place. The index will have pointers to the storage location data. A table can have more than one non-clustered index.

GAGANDEEP GAGAN
par GAGANDEEP GAGAN , secretary , smc global securities ltd

CLUSTER INDEX HAVE NO SEPRATE PLACE  REQUIRE TO SAVE A TABLE

BUT NON CLUSTER INDEX HAVE REQURIE SEPERATE PLACE TO SAVE A TABLE

sami baltagi
par sami baltagi , Management Consultant , PSS

one table can only have one clustered index.

one table can have many non-clusterd index.

A clustered index requires no seperate storage than the table storage, anon-clusterd index requires seperate storage than the table storage to store the index information.

ABDUL RAHMAN MANSOOR M
par ABDUL RAHMAN MANSOOR M , Network & System Administration – Engineer , ASPIRE SYSTEMS (India) Pvt Ltd

A clustered index actually describes the order in which records are physically stored on the disk, hence the reason you can only have one. A Non-Clustered Index defines a logical order that does not match the physical order on disk. A clustered index is essentially a sorted copy of the data in the indexed columns.

A C Handalage
par A C Handalage , Tech Lead/ Project Coordinator , Srila Systems Pvt LTD

Clustered Index

  • Only one per table (Promary Key)
  • Clustered indexes physically order the data on the disk
  • Accessing data using a clustered index is fastest.

Non Clustered Index

  • Can be used many times per table

A clustered index actually describes the order in which records are physically stored on the disk, hence the reason you can only have one. A Non-Clustered Index defines a logical order that does not match the physical order on disk

Rosmin.S Khan
par Rosmin.S Khan , Team Lead Software Engineer , -PBW Software Pvt Ltd

Index is special look-up table that database uses to speed up data retrieval. We have2 types of index > Clustered and non-clustered index.

clustered index - 

1). Can have only one clustered index on a table.

2). Doesn't allow null values.

3). Exists on physical level.

4). Assigned for primary keys.

5). Requires no separate storage than table storage.

 

Non-clustered index - 

1). We can have many clustered index (~).

2). allows null value.

3). Exists on logical level.

4). Assigned for unique keys.

5). Requires separate storage than table storage to store the index information.

Utilisateur supprimé
par Utilisateur supprimé

clustered index - Primary key to database. It can only be used 1 per table

 

non-clustered index - similarly to a foreign key. you can use it in multiple times in a multiple  table

Sirajuddin Mohammed
par Sirajuddin Mohammed , System Administrator , Advanced Program Trading

A clustered index actually describes the order in which records are physically stored on the disk

A Non-Clustered Index defines a logical order that does not match the physical order on disk.

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