Zusammenfassung der Ressource
Relational Databases
- File
- Table
- Record
- All data about one
person or thing.
- Quite a few fields can be
used to make a record e.g.
name, address,age,date of
birth.
- Field
- Primary Key
- A field in a table which is unique
and this helps to identify records
or people
- Referential integrity
- Every foreign key value has a
matching value in the
appropriate primary key field.
- A piece of data related
to a person or thing
- Foreign keys
- A primary key in one table inserted
as a normal field in another table
- Attributes-
Name,Age,Address
- Records are
stored in here.
- Made of quite a few pieces of
information, e.g. First Name,
Address, Age
- Entities-
objects,people,things
- RelationShips:
- One to Many
- Where one entity can have many
relations- such as 1 doctor has many
patient or 1 student has many exams
- Many to many
- where many entities can have many
relationships e.g. 1 video can be hired by
several customer BUT those customers can
hire several videos
- One to One
- When one entity can
only be related to one
entite e.g. 1 man has 1 wife.
- Many tables are stored in
a file, this is the database.
- Vast amounts of info can be stored!
- Queries can be run to search for specific records.
- Searching is what a query does.
- Parameters are just
search criteria
- 4 Types
- Static-the parameters
stay the same for ever.
- Dynamic- you can
change the search
result sto what you need
- Simple- only 1 parameter
is used at a time
- Complex-more
than one
parameter is used
- Reports can be created
from data stored or
queries run
- presents data taken from a query
or from tables in a preformatted
attractive manner
- Validation can be used to reduce errors.
- Validation!
- Makes sure that the data is:
accurate sensible,within
acceptable boundaries.
- Range Check- makes sure that
the value entered is between 2
preset boundaries
- Lookup Check-Allows only a limited
amount of item to be selected
- Length Check- checks that the data
entered is a certain length.
- Presence check- makes sure
something is enteredin the field
- NEVER MAKES SURE THAT
THE DATA IS CORRECT!!!
- Verification
- Making sure that the data on the
source document is the same as the
object doucument.
- Proof Reading- double checking your work basically.
- Double entry- where two people input the same
document and these are then compared any
differences are then noted and rectified.
- Forms Used to enter data.
- A window/Screen with multiple
spaces to enter data.