Databases

Question 1

What is a database table also known as?

Answer 1

An entity or file

Question 2

What is a record in a database? What are they also know as?

Answer 2

Records are the rows in a table
Known as rows/tuples

Question 3

What are fields in a database? What are they also known as?

Answer 3

Fields are the columns of a table
Also known as columns or attributes

Question 4

What is a flat file database?

Answer 4

One that only contains one table

Question 5

What methods are there of inputting data to a database?

Answer 5

• paper based, where a person types into a database based on a form
• optical text recognition, where a computer reads information
• optical mark recognition, e.g. multiple choice tests

Question 6

What methods are there of retrieving data from a database?

Answer 6

• SQL (SELECT FROM WHERE)
• QBE (visual tables where the user can enter commands and conditions, not syntax required)

Question 7

What methods are there of modifying data?

Answer 7

• DML (database manipulation language, using commands such as UPDATE, DELETE, INSERT)
• DBMS (database management system, hides the structure of the data to ensure integrity)

Question 8

What are the methods of exchanging data?

Answer 8

For recording data to transfer:
- XML, JSON
- comma separated values (CSV) in a notepad file

For exchanging files:
- memory stick, email etc. (Physical methods)
- Electronic data interchange (EDI), a protocol allowing two databases to interface

Question 9

What are the principles of 1NF?

Answer 9

• All field names must be unique
• All stored values in a field should be from the same domain (data type)
• Values in fields should be atomic (only one value)
• No two records can be identical
• Each table needs a primary key

Question 10

What are the principles of 2NF?

Answer 10

• The data is in 1NF
• Any partial dependencies have been removed (each table should be for one purpose, for example not a table of students and courses)

Question 11

What are the principles of 3NF?

Answer 11

• The data is in 2NF
• Any transitive dependencies are removed (all fields are dependent on the primary key, for example a table of course codes with lecturer names should not have lecturer initials as this is dependent on lecturer name, not course code)

Question 12

What is data integrity?

Answer 12

Ensuring the database contents are the same for all users

Question 13

What is referential integrity?

Answer 13

Ensuring data is consistent between fields in a relationship

Question 14

What is database atomicity?

Answer 14

Database transactions must be fully completed or not at all

Question 15

What is database consistency?

Answer 15

A change in the database must be retained by the database

Question 16

What is database isolation?

Answer 16

A transaction must not be interrupted by another transaction, it must occur in isolation ensuring other users cannot access the data

Question 17

What is database durability?

Answer 17

Once a change has been made, it must not be lost due to a hardware fault

Question 18

How would you do a join in SQL?

Answer 18

Select table1.data table2.data
From table1
Join table2
On table1.foreignkey = table2.primarykey
Where table1.field = condition