database

Cambrdige AS level computer science 2025. Textbook references: Cambridge International AS and A level computer science coursebook Sylvia Langfield, David Duddell 2019 press ||| Cambrdige International AS and A Levels Computer science by David Wastson, Helen Williams press 2019

what is a database

structured collection of items of data

how can a database be accessed

through different application programs

what is a relational database

where data items are linked by internal pointers

what is a table

group of similar data

what is a record

row in a table in a database

what is a field

column in a table in a database

what is a tuple

one instance of an entity represented in a row

what is an entity

anything that can have data stored about it

what are attributes

an individual data item stored for an entity

what is an example of attribute database for a human

name, address, date of birth

what is a candidate key

an attribute or smallest set of attributes in a table

what key represents no tuple having the same value

candidate key

what is a primary key

a unique identifier for a table

what is a secondary key

a candidate key that is an alternative to the primary key

what is a foreign key

a set of attributes in one table that refer to the primary key in another table

what is a relationship

one table in a database has a foreign key that refers to a primary key in another table in the database

what is referential integrity

does not contain any values of a foreign key that are not matched to the corresponding primary key

what is an index

built from one or more columns in a database table to speed up searching for data

what is entity-relationship model

a graphical representation of a database and the relationships between the entities

what does ER stand for

entity relationship

what is normalisation

organising data to be stored in a database into two or more tables and relationships between the tables

what does normalisation help with

data redundancy minimisation

what is first normal form

status of a relational database in which entities do not contain repreated groups of attributes

what does 1NF stand for

first normal form

what is second normal form

status of a relational database in which entities are in 1NF and any non-key attributes depend upon the primary key

what is third normal form

entities are in 2NF and all non-key attributes are independent

what is composite key

form a primary key to provide a unique identifier for a table

what does this picture show

entity relationship diagram

what is a file

collection of items of data

what can individual elements of data called

data items

what do you need to consider when changing a record in the another program

structure needs to be the same

what do you need to consider if you have to change the structure of a record when updating

you must rewrite the structure of others

what is the main issue with not storing with a file-based approach

inconsistency, redundant, non independent data

what is a word for an electronic filing cabinet

database

what can you do in a database

insert, retrieve, update, cross-reference data

what kind of database has internal pointers linking data items

relational database

which is better, database approach or fie-based approach

database approach

what makes database approach better

less storage used, no redundancy, independent data, consistent data

where are attributes on database tables

columns

where are entities on database tables

rows

What approach is this

File

What approach is this

Database

what should be thought of when trying to keep relational integrity

database must not contain values of a foreign key that are not matched in corresponding primary key

what are the form or relationships in databases

one to one

one to many

many to one

many to many

what are candidate key in a table

all attributes

what key is usually always there

primary key

if it isn’t primary key, what is it in a table

secondary key

what else is the primary key in a table

candidate key

what cardinality of relationships is this

one to one

what cardinality of relationships is this

one to many

what cardinality of relationships is this

many

what cardinality of relationships is this

one or more

what cardinality of relationships is this

one and one only

what cardinality of relationships is this

zero or one

what cardinality of relationships is this

zero or many

what symbol does this represent in databases

entities

what symbol does this represent in databases

attributes

what symbol does this represent in databases

relationships among entities

what symbol does this represent in databases

attributes to entities and entity sets with other relationship types

what symbol does this represent in databases

multi-valued attributes

what symbol does this represent in databases

weak entity

what is cardinality

number of elements in a set

what will happen to tables if they are not normalised

they will be larger with more data stored

what happens to data if it was not normalised in a table

becomes redundant

what is the problem of a non-normalised table

harder to update and difficult to extract data

what happens when you add data to a non-normalised table

you will have to change everything repeated everywhere manually

what can normalise tables

1NF, 2NF, 3NF

what does 1NF do

do not have repeated groups/attributes

what does 2NF do

any non-key attributes depend upon primary key and no partial dependencies

what does 3NF do

all non-key attributes are independent so there are no non-key dependencies

where are entitles in 2NF from

in 1NF

where are entities in 3NF from

2NF

mandatory or option cardinality? : one to many

mandatory

mandatory or option cardinality? : one or more

mandatory

mandatory or option cardinality? : one and only one

mandatory

mandatory or option cardinality? : zero or one

optional

mandatory or option cardinality? : zero or many

optional

what does it mean by optional cardinality

may or may not participate in a relationship with another entity

what does it mean by mandatory cardinality

must participate in a relationship with another entity

what is a compound key

two or more fields are needed to create a unique value

what does ASC mean in databases

ascending order

what does DESC mean in database

descending order

what does ORDER BY mean database

sorts data in ascending or descending

what does UPDATE do

change values in one or more columns

what does DBMS stand for

Database management system

what is DBMS

system software for creation and manipulation of a database

what is data management

organisation and maintenance of data in a database to provide the information required

what is data dictionary

set of data that contains metadata for a database

what is metadata

data about other data

what is data modelling

analysis and definition of the data structures required in a database and to produce a data model

what is logical schema

a data model for a specific database that is independent to DBMS used to build that database

what is access rights database

permissions given to database users to access, modify or delete data

what is developer interface

feature of a DBMS that provides developers with the commands required for definition, creation and manipulation of a database

what does SQL stand for

structured query language

what is SQL

language used with relational databases for data definition and data modification

what is query processor

features of a DBMS that processes and executes queries written in SQL

how does data redundancy issue get solved

storing data in separate linked tables

what issues does DBMS flag to improve data redundancy

accidental deletion or errors

how do you fix data inconsistency issue

storing most items only once

how do you fix data dependency issue

changes made have little or no effect on the applications using the database