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Generalized Projection Operation, Aggregation Operation

Generalized Projection Operation, Aggregation Operation

 

Let’s consider the following table and understand these operations with examples.

R1 :    FACULTY-1

FNoFNameDNoQualSalary
22Riya21Ph.D55000
24Priya22M. Tech50000
25Zayn22M. Tech42000
27Harry23M. Tech28000
30Sia23M. Tech32000
33Max24Ph.D53000
35Fred24Ph.D52000
37Diva25M. Tech26000
39Ben25M. Tech24000
40Trent25M. Tech34000

 

Generalized Projection Operation ( P ) : 

 

This operation allows arithmetic operations or string operations in the attribute list of projection operations.

 

Example-1 : Find the list of FName having PhD degree and their 10 %  of Salaries.

  P FName, Salary ¸ 10  (sQual = ‘PhD’ (Faculty-1)

 

Output :

FName10% x Salary
Riya5500
Max5300
Fred5200

 

Aggregation Operation : (   ) 

 

Aggregate Function takes a collection of values and returns a single value as a result.

 

 

Example-2 : Find the sum of the salaries of all the faculty.

 

   (Faculty-1)

   sum(Salary)

 

Output : 396000

 

Example-3 : Find the average of the salaries of all the faculty

 

 (Faculty-1)

 average(Salary)

 

Output :  39600

 

 

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