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Renames Operation ( ρ )

Renames Operation ( ρ ) 

 

Consider the following expression.

 ρx (E)

 

Here, this operator gives the name ‘x’ to the result of the relational algebra expression E.

 

Consider the following relation

R1 :    FACULTY-1

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

 

Example-1: Execute the following SQL expression.

   ρx (P Qual (Faculty-1) 

Output :    Qual

 Ph.D.

 MTech

Example-2 : Find the names of Ph.D. holders in a new relation named ‘F-PhD’.

ρ F-Ph.D. (P FName(squal  = ‘Ph.D.’ (Faculty-1) )

Output :    F-PhD

  FName

    Riya

 Max

 Fred

Example-3: Find the Salaries of  Ph.D. holders belonging to DNo = 24, under a new relation named ‘Sal-PhD-24’.

ρ Sal-PhD-24. (P Salary(squal  = ‘Ph.D.’ (Faculty-1) )˄ DNo = 24   

Output :  Sal-PhD-24  

  Salary

 53000

 52000 

 

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