SLR 10/ Databases Flashcards

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1
Q

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)

A

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

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

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2
Q

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

A

Atomicity
Durability
Isolation
Consistency

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3
Q

Define Atomicity

A

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

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4
Q

Define Durability

A

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

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5
Q

Define Isolation

A

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

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6
Q

Define Consistency

A

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.

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7
Q

Define Primary Key

A

A Unique Identifier for data in a database

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8
Q

Define a one to many relationship

A

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

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9
Q

Define one to one relationship

A

One field has only one relationship

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