Professor Materials Week 2

Question 1

What are the advantages of databases?

Answer 1

program/data independence
reduced data duplication
data consistency
data sharing
faster application development
standards enforcement
better data quality
improved accessibility
less maintenance

Question 2

What are the disadvantages of databases?

Answer 2

Database adminstrator and other specialized personnel needed
Installation and management costs
Conversion costs
need for explicit backup and recovery
organizational conflict

Question 3

What are the three types of database relationships?

Answer 3

One-to-one (rare)
one-to-many
many-to-many

Question 4

What is a weak entity?

Answer 4

An entity that cannot exist in a database i.e. an order that has no customer.

Question 5

What is a mandatory relationship?

Answer 5

A relationship that must exist, i.e. an order must have a customer.

Question 6

What is a composite entity?
E

Answer 6

Entities that exist to represent the relationship between two or more entitites.

Question 7

What are the two development approaches?

Answer 7

top-down (Start at general and drill down)
bottom-up (start with details and work up)

Question 8

What is the database development lifecycle?

Answer 8

1. Create a data model (E-R model)
2. Transpose data into relationships
3. Normalize relations
4. Implement the relational schema within a DBMS
5. Define forms, queries, reports, menus
6. Populate data
7. Maintenance

Question 9

What is the UoD?

Answer 9

Universe of Discourse, a short description of the subset or mdoel of reality that we are interested in implementing

Question 10

What is data modeling?

Answer 10

The process of determining what items are of importance to the users, rules that users need to be enforced and creating a model to capture that

Question 11

What is the schema?

Answer 11

Design for the database , including its tables, relationships, domains and constraints.

Syntax: RELATION_NAME(primary_key(underlined), attribute1, attribute2)