Indexing

Question

Answer 1

• Answer : B
• A clustered index determines the order in which the rows of the table will be stored on disk – and it actually stores row level data in the leaf nodes of the index itself. A non-clustered index has no effect on which the order of the rows will be stored.

• http://www.programmerinterview.com/index.php/database-sql/clustered-vs-non-clustered-index/

Comments

Clustering and Primary index are same? Please correct me if I'm going wrong somewhere.

In primary Index, ordering key field is used as key field.That is the key used to sort the records.

If the ordering key fields are not unique then a different key is used to index the records, this is

clustering indexing.In both cases records are order according to key (primary/clustered).

A file can have at most one physical ordering field, so it can have at most one primary index or

one clustering index, but not both.

Primary indexing is not same as clustering index right?

 

Excerpt from navathe.

A primary index is specified on the ordering key field of an ordered file of records. Recall from

Section 17.7 that an ordering key field is used to physically order the file records on disk, and

every record has a unique value for that field. If the ordering field is not a key field—that is, if

numerous records in the file can have the same value for the ordering field—another type of

index, called a clustering index, can be used.

---

Primary index

:in a sequentially ordered file, the index whose

  search key specifies the sequential order of the file.

            Also called clustering index

The search key of a primary index is usually but not

necessarily the primary key.

from:

https://www.cse.iitb.ac.in/~sudarsha/db-book/slide-dir/ch12.pdf

---

@Dharmendra Sir

See this:https://gateoverflow.in/85558/doubt-on-primary-indexing-and-clustred-index?show=85558#q85558

---

Clustered index : index on  ordering field.
Primary Index : Index on ordering field and also it should be key field.
so above statements we can conclude all primary index are clustered index but not vice-versa.

Secondary index : index on unordered field i.e. non-clustering index.
Sparse index : contains index records for only some search ­key values.
                          Applicable when records are sequentially ordered on search­ key.
Dense Index : Index record appears for every search ­key value in the file.