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GCSE Computer Science: Database
- Entity
- An entity is a person or
physical thing about
which data is held in a
database
- An entity is a person or
physical thing about
which data is held in a
database
- Field
- An individual
box in the data
table
- Table = The whole thing
- Table = The whole thing
- An individual
box in the data
table
- Record
- An entire row of
data
- An entire row of
data
- Database
management
system / DBMS
- Allows you to
create a table
- Componants
- Tables
- Forms
- Queries
- Reports
- Modules
- Program within an
application that
performs a specific
task which cannot be
done by simply
making a query or
report
- Program within an
application that
performs a specific
task which cannot be
done by simply
making a query or
report
- Tables
- Allows you to
create a table
- Datatypes
- Text
- Integers
- Numbers
with a
decimal
- Dates
- Currency
- Yes/No fields
- Text
- Primary Key
- One field is
designated as
the p.k
- Each record
must have a
different value
in the p.k
- Uniquely
identifies the
record
- One field is
designated as
the p.k
- Validating Fields
- Minimise errors
when data is
entered into the
database
- Specifying a
rule that the
data must obey
- Range check
- Type check
- e.g. number
- e.g. number
- Presence check
- Data entered
in the field
- Data entered
in the field
- Format check
- List check
- Must be item
on predefined
list
- Must be item
on predefined
list
- Range check
- Minimise errors
when data is
entered into the
database
- Data Redundancy
- Holding more
data than
necessary
- Takes time
and space
- Can result
in
inconsistent
data
- Can result
in
inconsistent
data
- Each entity has
an attribute
- Attribute =
Field in the
table which
describes
the entity
- One-to-one
- e.g. husband/wife
- e.g. husband/wife
- One-to-many
- e.g. mother/children
- e.g. mother/children
- Many-to-many
- e.g. pupils/subjects
- e.g. pupils/subjects
- One-to-one
- Attribute =
Field in the
table which
describes
the entity
- Holding more
data than
necessary
- Separation of Data
- Data held about
various entities
are held separatly
from the
applications that
use it.
- e.g. many
departments
in a school
can look at
or use the
data
- e.g. many
departments
in a school
can look at
or use the
data
- Reduces data
redundancy
- Data is consistent
- Saves storage
- Data held about
various entities
are held separatly
from the
applications that
use it.
- Database
- Persistent, organised store of data
- Persistent = Data
stored on a
non-volatile storage
device
- Organised =
Structured into tables
- Persistent = Data
stored on a
non-volatile storage
device
- Allows
separation of
data between
applications
and the
database
- Allows multiple
applications to use
a single database
- Can allow many
users to
simultaneously
access the data
and it's
applications
- Provides security in
terms of access
rights
- Can provide automatic backups
- Persistent, organised store of data
- Reports
- Useful feature of a DBMS
- Reports are
produed based
on queries
- When a user asks for a
report based on a query,
the query will
automatically be run first
using the latest data, so
the report is up-to-date
- Useful feature of a DBMS
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