SLR 10/ Databases

Question 1

Create an entity relationship diagram in 3nf for

Children’s swimming lessons at the local swimming pool

SWIMSCHOOL (member number, child name, contact number, class name, time of lesson, instructors name)

Answer 1

Members —————<Members>--------Class</Members>

Member Number Member Number Class name
Child name Class Name Time Lesson
Contact Num Instructor

Question 2

Database management systems have a set of rules to maintain referential integrity, known as ACID. What does this mean?

Answer 2

Atomicity
Durability
Isolation
Consistency

Question 3

Define Atomicity

Answer 3

A database change must be done completely or not at all. Databases must not become inconsistent due to partially completed transactions.

Question 4

Define Durability

Answer 4

Changes must not be lost. Records held in RAM are immediately saved to secondary storage – particularly important with multi-user databases.

Question 5

Define Isolation

Answer 5

Record locking prevents other processes from accessing the data when a record is being updated.

Question 6

Define Consistency

Answer 6

Attempting to add information in one table when matching relational data in another table does not exist would not be allowed. Records in related tables also need to be updated.

Question 7

Define Primary Key

Answer 7

A Unique Identifier for data in a database

Question 8

Define a one to many relationship

Answer 8

One field can have many relations. i.e one student can have many classes

Question 9

Define one to one relationship

Answer 9

One field has only one relationship