1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
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.

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

You might be interested in
Task 1 – File Input
e-lub [12.9K]

Answer:

Check the explanation

Explanation:

using System;

using System.IO;

                 

public class Program

{

 

  public static void Main()

  {

      string[] lines;

      Console.WriteLine("enter name of the file");

      String fileName=Console.ReadLine();

     

      Console.WriteLine("enter path of the file");

      String filePath=Console.ReadLine();

     

      using (StreamReader streamReader = File.OpenText(filePath))

      {

          String text = streamReader.ReadToEnd();

          lines = File.ReadAllLines(filePath);

      }

      Console.WriteLine("Enter path of the file to write");

      String outputFilePath = Console.ReadLine();

      bool fileExist = File.Exists(outputFilePath);

      if (fileExist)

      {      

                  overWriteOrChangeFileName(outputFilePath);          

      }

      else

      {

          File.Create(outputFilePath);

          File.WriteAllLines(outputFilePath, lines);

      }

      Console.Write("Input file Path"+filePath);

      Console.Write("output file path"+outputFilePath);

     

      void overWriteOrChangeFileName(String filePathtoCheck){

          Console.WriteLine("File exists. Do you want to overwrite the file or do you want to change the location and file name of the new file.Press Y to overwrite and press C to change the location and filename");

          String userInput=Console.ReadLine();

          if(userInput.Equals("Y")){

File.WriteAllLines(outputFilePath, lines);

          }else{

              Console.WriteLine("enter new path of the file including filename");

              String NewFileName=Console.ReadLine();

              outputFilePath=NewFileName;

              if(File.Exists(outputFilePath)){

                  overWriteOrChangeFileName(outputFilePath);                  

              }

              else

      {

          File.Create(outputFilePath);

          File.WriteAllLines(outputFilePath, lines);

      }

          }

      }

  }

 

}

3 0
4 years ago
What is the name of the computer through which e-mail messages are sent and received?
nalin [4]
A mail server. --------------------------------------------
8 0
3 years ago
Mention any four features which a standard computer laboratory should have​
Vera_Pavlovna [14]

Answer:

•Make sure doorway openings are at least 32 inches wide and doorway thresholds are no higher than 1/2 inch.

•Keep aisles wide and clear for wheelchair users.

•Make sure all levels of the lab are connected by a wheelchair-accessible route of travel.

For students with mobility impairments, make sure there are procedures in place for retrieving materials that may be inaccessible.

Make sure ramps and/or elevators are provided as an alternative to stairs. Elevators should have both auditory and visual signals for floors. Elevator buttons should be marked in large print and Braille or raised notation and easily reachable for wheelchair users.

Locate the lab near wheelchair-accessible restrooms with well-marked signs.

Service desks need to be wheelchair-accessible.

Provide ample, high-contrast, large-print directional signs throughout the lab. Mark equipment in the same fashion.

Provide study carrels, hearing protectors, or private study rooms for users who are easily distracted by noise and movement around them.

Provide at least one adjustable-height table with easily reachable controls for each type of computer.

Have wrist rests available to those who require extra wrist support while typing.

Keep document holders available to help users position documents for easy reading.

5 0
3 years ago
Read 2 more answers
_____ regulate current/voltage flow, similar function as _____,but are smaller, cheaper, and more reliable.
Tpy6a [65]

Direct Current Power regulates current/voltage flow, similar function as unregulated or regulated, but is smaller, cheaper, and more reliable.

<h3>What is Direct Current Power?</h3>
  • In contrast to the flow of a river, direct current is a technique in which electricity constantly flows in the same direction. It speaks about the flow of electricity produced by batteries, solar cells, and other sources.
  • Alternating current (AC), on the other hand, is a technique in which the positive and negative sides are consistently swapped at regular intervals, changing the direction of the electricity flow in accordance.
  • This is the electricity that comes from a generator or a plug-in.
  • Alternating current is used to transmit both the electricity generated at power plants and the electricity delivered to houses.

To learn more about Direct Current Power, refer:

brainly.com/question/1402412

#SPJ4

8 0
2 years ago
National Computer Corporation (NCC) employs Cynthia as an agent. NCC gives her an exclusive territory in which to sell NCC produ
LuckyWell [14K]

Answer:

The answer is cooperation

Explanation:

National Computer Corporation (NCC) employs Cynthia as an agent. NCC gives her an exclusive territory in which to sell NCC products. NCC cannot compete with her in that territory under the duty of cooperation

8 0
3 years ago
Other questions:
  • Write a Console Java program that asks the user to enter one sentence on the keyboard. Output on the console:
    6·1 answer
  • How hot is to hot for my computer?
    11·2 answers
  • Briley has all the hardware she needs to construct a fully functional personal computer. She connects the various components and
    7·1 answer
  • i have a class for computers and i need a free hardrive are there any websites that give me one for free in 3 days??​
    15·1 answer
  • Write a python program to accept a number and check whether it is divisible by 4 or not​
    10·1 answer
  • Which company was the first to develop personal computers?
    6·1 answer
  • PLEASE HELP
    14·1 answer
  • True or False The two types of general construction projects are residential for homes or dwellings and commercial for a commerc
    7·1 answer
  • What are general purpose computer and special purpose computer?​
    10·2 answers
  • How can we search person in brainly for sending request of friend
    10·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!