1.3.2 - Databases

Question 1

Relationships

Answer 1

One-to-one
One-to-many
Many-to-many

Question 2

Primary Key

Answer 2

Unique identifier for a table
Defined underlined
Indexed for quick searching

Question 3

Secondary Key

Answer 3

Not a unique identifier but something that is searched frequently so is indexed for ease

Question 4

Foreign Key

Answer 4

Field in a table that is the primary key of another table in the relational database
Defined in italics

Question 5

Referential integrity

Answer 5

The foreign key in one table must reference the primary key of another table

Question 6

Normalisation

Answer 6

Finding best possible design for database

Question 7

Features of normalised database

Answer 7

Easier to maintain
No unnecessary duplication of data
Data integrity
Faster searches

Question 8

Features of a table in 1NF

Answer 8

All data is atomic
Data within fields are of the same type
Fields have unique names

Question 9

Features of table in 2NF

Answer 9

All of 1NF
No partial dependencies

Question 10

Partial dependency

Answer 10

Attribute depends only on a part of a composite key rather than the whole thing

Question 11

Properties of table in 3NF

Answer 11

All of 2NF
No transitive dependencies

Question 12

Transitive dependency

Answer 12

Attribute is only dependent on the primary key, not anything else

Question 13

Methods of capturing data

Answer 13

Manual
Automated

Question 14

Methods of transferring data

Answer 14

Automatically using DBMS
Using EDI - electronic data interchange -> replaces email/fax

Question 15

Transaction

Answer 15

Single logical operation on a database

Question 16

ACID

Answer 16

Atomicity
Consistency
Isolation
Durability

Question 17

Atomicity

Answer 17

All or none of the transaction is processed

Question 18

Consistency

Answer 18

Defined rules of the database cannot be violated

Question 19

Isolation

Answer 19

Concurrent execution of different transaction leads to same result

Question 20

Durability

Answer 20

Transaction must be processed and saved

Question 21

Record locking

Answer 21

Prevents simultaneous access to documents

Question 22

Problem with record locking

Answer 22

Deadlock when two or more processes lock a record the other needs so neither can complete

Question 23

Timestamp ordering

Answer 23

A transaction can only complete if the most recent open of the database is the same as the user, if not someone else has opened more recently

Question 24

Redundancy

Answer 24

Back up copy of data, often stored in a different physical location