This topic contains a solution. Click here to go to the answer
« previous next »

Author Question: How is a composite attribute of an entity mapped into a relation? What will be an ideal ... (Read 53 times)

bcretired

  • Hero Member
  • *****
  • Posts: 525
on: Jul 7, 2018
How is a composite attribute of an entity mapped into a relation?
 
  What will be an ideal response?

Question 2

What is a primary key?
 
  What will be an ideal response?


Related Topics

Need homework help now?

Ask unlimited questions for free

Ask a Question
Marked as best answer by a Subject Expert

31809pancho

  • Sr. Member
  • ****
  • Posts: 317
Reply #1 on: Jul 7, 2018
Answer to Question 1

If an entity contains composite attributes, each component of the composite attribute is mapped as a column of a relation, while the composite attribute itself does not appear in the mapped relation.

Answer to Question 2

Primary key is a column (or a set of columns) whose value is unique for each row. Primary keys cannot have null values. If there are multiple columns (or sets of columns) that have unique values in each row, one of them is designated as a primary key. Each relation must have a primary key.


bcretired

  • Member
  • Posts: 525
Reply 2 on: Jul 7, 2018
YES! Correct, THANKS for helping me on my review

alexanderhamilton

  • Member
  • Posts: 334
Reply 3 on: Yesterday
Excellent

« previous next »
 

Did you know?

Cucumber slices relieve headaches by tightening blood vessels, reducing blood flow to the area, and relieving pressure.

Did you know?

Prostaglandins were first isolated from human semen in Sweden in the 1930s. They were so named because the researcher thought that they came from the prostate gland. In fact, prostaglandins exist and are synthesized in almost every cell of the body.

Did you know?

Medication errors are more common among seriously ill patients than with those with minor conditions.

Did you know?

A good example of polar molecules can be understood when trying to make a cake. If water and oil are required, they will not mix together. If you put them into a measuring cup, the oil will rise to the top while the water remains on the bottom.

Did you know?

The calories found in one piece of cherry cheesecake could light a 60-watt light bulb for 1.5 hours.

The Mass-Luminosity Relation The Mass-Luminosity Relation
The relation between drug tolerance and withdrawal effects. The same adaptive neurophysiological ... The relation between drug tolerance and withdrawal effects. The same adaptive neurophysiological ...
How to find the maximum and minimum of a quadratic relation How to find the maximum and minimum of a quadratic relation
How to write a composite function f(g(x)) and g(f(x)) (Part 2) How to write a composite function f(g(x)) and g(f(x)) (Part 2)
Under ideal conditions, a single cell of the bacterium E. coli would divide every 20 minutes to ... Under ideal conditions, a single cell of the bacterium E. coli would divide every 20 minutes to ...
Video: Elementary kinetics

For a complete list of videos, visit our video library