DATABASES

Question 1

What is a DB

Answer 1

persistent and structured collection of data

Question 2

What is a record

Answer 2

Single unit in a database, made up of fields (name ,Id,etc)

Question 3

What is a transaction

Answer 3

Change in state of a database

Question 4

What is transaction file

Answer 4

A file of events

Question 5

What is a master file

Answer 5

Principal file that stores basic details about a business (eg supermarket stock)

Question 6

What is a flat file database

Answer 6

One table in the database, no other tables

Question 7

What is a entity

Answer 7

Any thing represented in a database like a student or bag

Question 8

What is a relational database

Answer 8

Database with one or more tables with unique keys to provide a relations between data

Question 9

What is a tuple

Answer 9

Same as record

Question 10

What is a primary key

Answer 10

Unique key to a row

Question 11

What is a foreign key

Answer 11

A field repeated from another table

Question 12

What is a secondary key

Answer 12

Additional key used with the primary key to locate a piece of data, narrowing down the data. It’s not unique but it is unique to a smaller number of fields making the search possibly faster

Question 13

What is data redundancy

Answer 13

Unnecessary repeated data

Question 14

What is database normalisation

Answer 14

Where collection of data is gradually (in 3 steps) organised into tables to remove data redundancies

Question 15

Requirements for 1NF

Answer 15

No duplicate columns
Has primary key
Data is atomic

Question 16

Requirements for 2NF

Answer 16

1NF

every field is dependent on the primary key

Question 17

Requirements for 3NF

Answer 17

2NF
No transitive dependencies, fields cannot depend on a non key field

NO MANY TO MANY RELATIONSHIPS

Question 18

What is a composite key

Answer 18

Combination of multiple keys, eg first and surname

Question 19

What does CRUD mean in a RDB

Answer 19

DB must be able to have create read update and delete rows

Question 20

What is transaction processing

Answer 20

Processing which provides a response to a user in a short time

Question 21

What is data integrity

Answer 21

Data is intended and is fit for purpose

Question 22

What is meant by referential integrity [2]

Answer 22

Ensuring that changes in a database are consistent (so) if a record is removed all references are also removed

Question 23

What are the ACID rules in a database

Answer 23

ATOMICITY - changes in a database are performed, or not performed
CONSISTENCY - constant state of the database before and after
ISOLATION - transactions are performed in isolation, so nothing can interrupt it, only until data has been committed
DURABILITY - once A change is made is must not be lost

Question 24

SQL to select name and address from customer table , where the name must be cox

Answer 24

SELECT “NAME”, “ADDRESS” FROM “Customers” WHERE “Name” = “Cox”;

Question 25

SQL to select all columns from customer table where the address ends with Street

Answer 25

SELECT * FROM “CUSTOMERS” WHERE “ADDRESS” LIKE “%Street”

Question 26

2 problems with flat file

Answer 26

Data redundancy

Inconsistent data

Question 27

SQL to select video name from videos table where name is hi

Answer 27

SELECT VideoName FROM Videos WHERE VideoName = “hi”

MUST USE CORRECT QUOTES

Question 28

SQL to delete row from table

Answer 28

DELETE FROM [table] ….