« previous next »

Author Question: What is a relational database model? How do relations differ from nonrelation tables? What will ... (Read 109 times)

HCHenry

  • Hero Member
  • *****
  • Posts: 591
on: Jul 7, 2018
What is a relational database model? How do relations differ from nonrelation tables?
 
  What will be an ideal response?

Question 2

The ________ defines the number of instances of entity B that can (or must) be associated with each instance of entity A.
 
  A) Cardinality
  B) Relationship
  C) Identifier
  D) Association
Modern Systems Analysis and Design ¦ Valacich, George ¦ 8th Edition
Buy Test-Bank


ebonylittles

  • Sr. Member
  • ****
  • Posts: 318
Reply #1 on: Jul 7, 2018
Answer to Question 1

The relational database model represents data in the form of related tables, or relations. A relation is a named, two-dimensional table of data. Each relation (or table) consists of a set of named columns and an arbitrary number of unnamed rows. Each column in a relation corresponds to an attribute of that relation. Each row of a relation corresponds to a record that contains data values for an entity. Relations have several properties that distinguish them from nonrelational tables: 1. Entries in cells are simple. An entry at the intersection of each row and column has a single value. 2. Entries in a given column are from the same set of values. 3. Each row is unique. Uniqueness is guaranteed because the relation has a nonempty primary key value. 4. The sequence of columns can be interchanged without changing the meaning or use of the relation. 5. The rows may be interchanged or stored in any sequences.

Answer to Question 2

A


Related Topics

Need homework help now?

Ask unlimited questions for free

Ask a Question
« previous next »
 

Did you know?

Blood in the urine can be a sign of a kidney stone, glomerulonephritis, or other kidney problems.

Did you know?

The liver is the only organ that has the ability to regenerate itself after certain types of damage. As much as 25% of the liver can be removed, and it will still regenerate back to its original shape and size. However, the liver cannot regenerate after severe damage caused by alcohol.

Did you know?

A cataract is a clouding of the eyes' natural lens. As we age, some clouding of the lens may occur. The first sign of a cataract is usually blurry vision. Although glasses and other visual aids may at first help a person with cataracts, surgery may become inevitable. Cataract surgery is very successful in restoring vision, and it is the most frequently performed surgery in the United States.

Did you know?

The lipid bilayer is made of phospholipids. They are arranged in a double layer because one of their ends is attracted to water while the other is repelled by water.

Did you know?

People often find it difficult to accept the idea that bacteria can be beneficial and improve health. Lactic acid bacteria are good, and when eaten, these bacteria improve health and increase longevity. These bacteria included in foods such as yogurt.

Model Organism Neurospora Model Organism Neurospora
This chart shows the various lines of responsibility and how they differ in presidential and parliam This chart shows the various lines of responsibility and how they differ in presidential and parliam
Model for induction of B. subtilis tyrS gene by uncharged tRNATyr Model for induction of B. subtilis tyrS gene by uncharged tRNATyr
Descartes's model of simple reflexes Descartes's model of simple reflexes
A polygenic model for a threshold trait A polygenic model for a threshold trait
The X-linked genetic model of Morgan’s eye-color inheritance The X-linked genetic model of Morgan’s eye-color inheritance
Video: Rods and Cones Animation

For a complete list of videos, visit our video library