Horizontal fragmentation in Distributed Database System

Horizontal fragmentation in Distributed Database System

Partitions a table along its tuples is performed based on some Predicate/ Condition

Consists of a subset of the tuples of a relation.

Defined using Selection Operation of relational Algebra

s_predicate (R)

F1 = s_{city = ‘Lahore’} (Employee)

F1 = s_{city = ‘Karachi’} (Employee)

Horizontal Fragmentation Example

CREATE TABLE employee(

emp_no INTEGER PRIMARY KEY,

emp_name CHAR(20) NOT NULL,

City CHAR(20) NOT NULL,

salary int

)

 insert into employee values(1,'Asad','Lahore',18000)

 insert into employee values(2,'hafeez','karachi',20000)

 insert into employee values(3,'Wasiq','Lahore',30000)

 insert into employee values(4,'Sohail','Lahore',50000)

 insert into employee values(5,'Atif','Peshawer',45000)

 insert into employee values(6,'Naveed','Multan',55000)

 insert into employee values(7,'Manawar','Karachi',80000)

 insert into employee values(8,'Adnan','Peshawar',70000)

 insert into employee values(9,'Ahir','Multan',45000)

 insert into employee values(10,'Aslam','Peshawer',90000)

 insert into employee values(11,'Abdullah','Multan',55000)

 insert into employee values(12,'Salman','Karachi',80000)

 insert into employee values(13,'Fitama','Peshawar',70000)

 insert into employee values(14,'Shahbaz','Multan',45000)

 insert into employee values(15,'sultan','Peshawer',90000)

Select * From Employee

Create Fragment 1

select *  into employee1 from employee where city = 'Multan'

select * from employee1

Create Fragment 2

select * into employee2 from employee where city = 'Lahore'

select * from employee2

Create Fragment 3

select * into employee3 from employee where city = 'Karachi'

select * from employee3

Create Fragment 4

select * into employee4 from employee where city = ‘Peshawer'

select * from employee4

Combine All Four Fragment 

select * from employee1 

union all

select * from employee2 

union all

select * from employee3

 union all

select * from employee4