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maxonik [38]
3 years ago
9

Consider the relational schema below: Students(sid: integer, sname: string, major: string) Courses(cid: integer, cname: string,

hours: integer) Enrollment(sid: integer, cid: integer, grade: real) Write a relational algebra expression that satisfies this query? Find the distinct names of all students that take at least three courses and major in "Philosophy".
Computers and Technology
1 answer:
daser333 [38]3 years ago
7 0

Solution :

Here, we need to perform JOIN operation of the students and registration.

Use NATURAL JOIN operator \Join and so no need to specify Join condition.

Also we need to selection operator tp select only those course whose major in "philosophy".

Finally we projection operator π to project only distinct students name who took at least three courses.

$\pi [\sigma_{\text{student's nam}e} [ \sigma(\text{three courses}) \Join \text{"Philosophy"}]]$

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Fiesta28 [93]

Answer:

import java.util.Scanner;

public class num2 {

   public static void main(String[] args) {

       Scanner in = new Scanner(System.in);

       int count =0;

       int total = 0;

       System.out.println("Enter the numbers");

       int num = in.nextInt();

       while(num!=-1){

           total = total+num;

           count++;

           System.out.println("Enter the next number");

           num = in.nextInt();

       }

//Compute the average

       double average = (double) total/count;

//Outputs

       System.out.println("Total count of numbers entered "+(count));

       System.out.println("Sum of the numbers "+total);

       System.out.printf("Average is %.2f ",average);

   }

}

Explanation:

  • Using java programming language
  • Import scanner class to receive user input
  • declare variables count and total and initialize to zero
  • Prompt user to enter numbers
  • Use a while statement with the condition while(num!=-1)
  • Within the while body keep prompting user to enter a number, increase count and update total
  • when -1 is entered the loop breaks and average is calculated
  • Use printf() method to print average to 2 decimal places.
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LenKa [72]

Answer:

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olga_2 [115]

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Lacking a response to my question, I'll assume there's no "correct' answer here. 

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Answer:

3

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