1.3.2 Databases - Atharwa

Question 1

What is an Entity?

Answer 1

An item, object or thing a database is about

Question 2

What is a flat-file database?

Answer 2

A database where data is all stored on one large table

Question 3

What is a relational database?

Answer 3

Data stored in separate tables linked with foreign keys

Question 4

What is a Primary key?

Answer 4

A field which can be used to uniquely identify a record

Question 5

Name ways of collecting data

Answer 5

Webforms, Barcodes, QR codes, Written forms with optical character recognition, Magnetic ink/ stripes

Question 6

What are the requirements of 1NF?

Answer 6

Must have a primary key, data must be atomic, no repeating attributes, each field must a unique.

Question 7

What are the requirements of 2NF?

Answer 7

Must be in 1NF, no partial dependencies.

Question 8

What are the requirements of 3NF?

Answer 8

Must be in 2NF, no transitive dependencies.

Question 9

What is a partial dependency?

Answer 9

When a field only depends on a part of a composite key, not all of it.

Question 10

What is a transitive dependency?

Answer 10

When a field depends on another field that isn’t a primary/composite key

Question 11

What is a transaction?

Answer 11

A change made to a database.

Question 12

What is meant by Atomicity?

Answer 12

A transaction must be fully completed for it to be recorded.

Question 13

What is meant by Consistency?

Answer 13

Any changes made must not break the database, keeping it consistent with how it was before.

Question 14

What is meant by Isolation?

Answer 14

A transaction must be kept isolated so it doesn’t interfere with other transactions.

Question 15

What is meant by Durability?

Answer 15

A transaction must remain in the database once saved

Question 16

What is meant by Data Integrity?

Answer 16

Data integrity is making sure that data remains accurate, complete and consistent, without being lost, changed or corrupted.

Question 17

How is Data integrity maintained?

Answer 17

Use of validation and verification.

Question 18

What is Referential Integrity?

Answer 18

the principle of ensuring that relationships between linked database tables remain valid, consistent, and accurate

Eg. Ensuring that an order cannot be placed if the customer does not exist in the customer table

Question 19

What is Redundancy?

Answer 19

Multiple clones of the same database kept at different places with backups to use if one of them is lost

Question 20

Name 3 relationships used in an entity relationship diagram

Answer 20

1 to many, many to many, many to one

Question 21

What is ACID

Answer 21

Atomically
Consistency
Isolation
Durability