horizontal fragmentation, Database Management System

Assignment Help:

Horizontal Fragmentation-Horizontal fragmentation groups together the tuples in a relation that are collectively used by the main transactions. A horizontal fragment is produced by specifying a WHERE clause condition that shows a restriction on the tuples in the relation. It can also be described using the Selection operation of the relational algebra.

Example:

Let us demonstrate horizontal fragmentation with the help of an example.

 DEPOSIT (branch-code, account-number, customer-name, balance)

A sample relation instance of the relation DEPOSIT is shown in Figure.

Branch-code

Account number

Customer name

Balance

1101

3050

Suresh

5000

1101

2260

Swami

3360

1102

1170

Swami

2050

1102

4020

Khan

10000

1101

1550

Khan

620

1102

4080

Khan

1123

1102

6390

Khan

7500

                                                              Figure: Sample DEPOSIT relation

Mathematically a fragment may be described as a selection on the global relation R. The reconstruction of the relation R can be taken by taking the union of all fragments.

So let us decay the table in Figure into horizontal fragments. Let us do these fragments on the branch-code as 1101 and 1102

DEPOSIT1 obtained by selection on branch-code as 1101

Branch-code

Account number

Customer name

Balance

1101

3050

Suresh

5000

1101

2260

Swami

3360

1101

1550

Khan

620

DEPOSIT2 obtained by selection on branch- code as 1102

Branch-code

Account number

Customer name

Balance

1102

1770

Swami

2050

1102

4020

Khan

10000

1102

4080

Khan

1123

1102

6390

Khan

7500

 

 

 

 

 

 

 

 

 

                                        Figure: Horizontal fragmentation of relation DEPOSIT

 

The two fragments can be described in relational algebra as:

 

DEPOSIT1 = σ branch-code= 1101 (DEPOSIT)

DEPOSIT2 = σ branch-code= 1102 (DEPOSIT)

These two fragments are given in Figure. Fragment 1 can be stored in the branch whose code is 1101 whereas the second fragment can be stored at branch 1102.

In our example, the fragments are disjoint. Though, by changing the selection predicates used to construct the fragments; we may have overlapping horizontal fragments. This is a type of data replication.


Related Discussions:- horizontal fragmentation

The average amount of their orders , Make SQL statements for the following ...

Make SQL statements for the following scenarios. Your response should contain SQL statement, output and any other assumptions you have made to arrive at the answer. For Colorado cu

Tables, does tables are called relations

does tables are called relations

What is stored procedure, What is Stored Procedure? A stored procedure ...

What is Stored Procedure? A stored procedure is a named group of SQL statements that have been previously formed and kept in the server database. Stored procedures accept input

Implementation of association as an object, Implementation of association a...

Implementation of association as an object Implement as a separate association object, independent of either class, as in Figure. An association object is a group of pairs

Illustrate the collaboration and relationship diagram, Illustrate the colla...

Illustrate the collaboration and relationship diagram A collaboration is the society of interfaces, classes and other elements which work together to provide some cooperative b

System level permissions-data control, System level permissions : With the ...

System level permissions : With the use of data dictionary you can view them.       Let us take the table name as user_sys_privs (used in oracle).       DESCRIBE USER_SYS_PRI

Define granularity and hierarchy of granularity of locks, Define granularit...

Define granularity, hierarchy of granularity of locks & multiple granularity locking. Explain the modified two phase locking along with multiple granularity locking. Ans: The s

Explain the recoverable schedule, Explain the Recoverable Schedule A r...

Explain the Recoverable Schedule A recoverable schedule is one in which for each pair of transactions Ti and Tj such that Tj reads a data item formerly written by Ti, the comm

Define control files, Control Files : The redo and control files logs supp...

Control Files : The redo and control files logs support the rest of the architecture. Every database must have at least one control file, although you have more than one to guard

What are composite objects, What are composite objects? Objects that ha...

What are composite objects? Objects that have other objects are known as complex objects or composite objects.

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd