# Indexing

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A file is organized so that the ordering of data record is same as or close to the ordering of data block in some index. Then that index is called:-

1. Dense
2. Sparse.
3. Clustered
4. Unclustered

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A Clustered index is a special type of index that reorders the way records in the table are physically stored. Therefore table can have only one clustered index. With a clustered index the rows are stored physically on the disk in the same order as the index.  You can have only one clustered index per table because this defines how the data is physically arranged. A clustered index means you are telling the database to store close values actually close to one another on the disk. This has the benefit of rapid scan / retrieval of records falling into some range of clustered index values.

A clustered index created on any key column(s)  will enforce an ordering on the rows of table. All the rows will be stored in sorted manner on the key column used to create the clustered index.

Say You want to make an Index on some Ordered field then you can make either Sparse or Dense Index. No problem. We can Always make Dense index for any field(s).

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Yes sir but answer given by made easy is sparse indexing :(
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Sparse index could be the second choice for the answer because we make Sparse index for Ordered field only. But, Clustered index seems to be the best choice as it is defined in this way only. What is given in the Question is the definition of Clustered index.
• Option a is right . It is a defination of dense .
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Sir one more thing why its not clustered index because in clustered index the order of index record blocks is in the order of records in database. right ?
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it is not a sparse indexing.i think answer should be wrong.

http://www.cs.sfu.ca/CourseCentral/354/zaiane/material/notes/Chapter11/node5.html

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Sir why its not Clustered Indexing ???

because in clustered index the order of index record blocks is in the order of records in database. right ?
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because in clustered index the order of index record blocks is in the order of records in database. right ?

Right.

in my point of view, { Dense, Sparse } and { key, non-key } both are different sets

we use

1) key + file is ordered by key ===> uses Sparse Index ===> Primary Index

2) non-key+ file is ordered by non-key ===> uses Sparse Index ===> Clustered Index

3) non-key+ file is not ordered by non-key ===> uses Dense Index ===> Non-Clustered Index

4) key+ file is not ordered by key ===> uses Dense Index ===> Secondary Index

ordering of data record is same as or close to the ordering of data block in some index it can be primary index or clustered index

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