Primary index

Primary index / Primary indexing / Clustered index / Clustering index / index sequential file

An index whose order of the entries is same as the order of the records in the database table file is called as primary index. It can also be referred as clustering index, or clustered index.

Primary or clustering index’s search key is often the primary key of the table. It is not compulsory to have primary key attribute as the primary index’s search key. We can have other attributes as well.

Points to know about primary index:

• A Primary Index forces a sequential file organization on the Data File;

• Since a Data File can have just one order there can be just one Primary Index for Data File

• The combination of a sequentially ordered file plus a clustering index is an index-sequential file

Primary index example:

In this example, the left side table is the index table, and the right side is the Students table. The search key or the ordering key field in the index table is the register number of students, which is the primary key of the students table. Observe from the picture given below the order of both index and the data file are the same.

Primary index (dense) example

A primary index (clustering index or clustered index or index on sequential files) can be one of two of the following types;

• Dense index

• Sparse index

 


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Database Index

Database Index / Define index in database / What is index? / Example of an index / Purpose of a database index

Index

An index is an auxiliary data structure that is used to find records that meet a selection condition. Index is used especially to speed up the selection process where a selection condition to be verified on records. Index works the same way as the indexes found in end of the pages of most of the books.

Some of the indexes that you might have used are,

• Card catalog in libraries
• Telephone directory
• Book last page indexes

Example

Book last page index

We can easily observe from the above image about an index. Yes, it has certain properties;

Index is sorted

Each entry (ex. Basic operation 14) contains the page number along with it

All the index keys are listed.

This type of arrangement speeds up our process by directly giving us the page where the required data are available.

Indexes usually are of two broad types. They are;

• Ordered indices – sorted values
• Hash indices – distribution based on hash function

You can click on "How to choose the type of index for your application" to know about applications where these types can fit.

Database Index - Hash Index

Hash Indexes

To be continued...




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Database Index - Ordered Index

Ordered indexes / What is an ordered index? / Types of ordered index

Ordered indices

An index that is sorted and stored on its search key value is called as ordered index. For example, if you consider any book’s last page indexes, you would see that they are ordered on the topics. It makes us easy to visit the content related to the topic by searching in alphabetical order.

The ordering or sorting in ordered indices would mean two things;

1. Ordering of the index – that is, the search key values that are stored as part of the index file is ordered.
2. Ordering of the file in which the table or relation is stored – that is, the actual database records that are stored in a file in the same order as the index entries order.

The first one may be primary or secondary type indices (it depends on the ordering of the database file).

The second one is strictly a primary index.

A database file may have several indices depends on their requirements. These indices can be one of the following types;

• Primary index

• Secondary index

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MC 7103 – DATABASE MANAGEMENT SYSTEMS May June 2014 Question Paper

MC 7103 – Database Management Systems - May/June 2014 Question Paper / Anna University MCA Exam May/June 2014 Question Paper / MC7103 DBMS May/June 2014 Question Paper / MC7103 Database Management Systems Previous Year Question Paper with Answers / Anna University Affiliated Colleges MCA Question Papers / Regulation 2013 MC7103 Question Paper

Question Paper Code : 60804

M.C.A DEGREE EXAMINATION, MAY/JUNE 2014

MC 7103 – DATABASE MANAGEMENT SYSTEMS

(Regulation 2013)

Time : Three Hours                                                         Maximum : 100 marks

Answer ALL Questions

PART A – (10 X 2 = 20 marks)

1. What do you mean by weak entity set?

2. List any four applications where database is used.

3. With an example define the basic structure of a relational database.

4. For the given schema structure – loan(loan_number, branch_name, amount), using Tuple Relational Calculus, find the loan number with amount greater than Rs.50,000.

5. Define the term ACID property.

6. What is shadow paging?

7. Mention the advantages and disadvantages of indices.

8. Why variable length records arises in databases? Give an example.

9. What are the advantages of OODBMS?

10. Write a note on nested relation.

PART B – (5 X 16 = 80 marks)

11. (a) Explain the database system architecture with neat diagram. (16)

Or

(b) (i) Draw the ER diagram for University database and explain each attribute in detail. (8)

(ii) Discuss the various disadvantages of file system and explain how it can be overcome by DBMS. (8)

12. (a) Explain Boyce Codd Normal Form and 3NF with your own example. Also give how it differs from that of 3NF. (16)

Or

(b) Explain various relational algebra operators with suitable example. (16)

13. (a) Explain the different techniques of serializability with example. (16)

Or

(b) How concurrency control is performed? Explain the protocol that is used to maintain the concurrency concept. (16)

14. (a) Explain how B+ tree is used for indexing with an example. (16)

Or

(b) Construct the extendible hash structure to accommodate the records of a relation given below by using the search key values given. (Assume the bucket size as 2) (16)

A217 A101	Brighton Downtown	750 500
A110	Downtown	600
A215	Mianus	700
A102	Perryridge	400
A201 A218	Perryridge Perryridge	900 700
A222	Redwood	700
A305	Round Hill	350

Table

Branch_name	h(branch_name)
Brighton Downtown Mianus Perryridge Redwood Round Hill	0010 1101 1111 1010 0011 1010 1100 0111 1110 1111 0001 0010 0011 0101 1010 1101 1000 0011

Search key values

15. (a) Explain the following with example.

          (i) Spatial databases. (8)

          (ii) For given RDBMS schema (s_id integer, s_name string, s_status string), give the equivalent XML schema structure. (8)

Or

(b) Design a database for the student management system with the requirements like managing attendance details and the semester marks of the students. Give the complete design that includes ER diagram, relational databases using normalization. (16)

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