Transcript Database Principles & Structures

UNIT 16 DATABASE
SYSTEMS
Lynda Spencelayh
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P1 -Principles of a
Database System
Explain the principles of a database
system, consider the advantages &
disadvantages of using databases.
Ensure you identify at least two
advantages and two disadvantages- base
these on your case study.
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Principles of database
systems
Give examples can include - how the
database system you have created
supports the college / tutor.
Include benefits using database tools
[queries, forms, reports & macros - such
as buttons]
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Principles of database
systems
Databases are everywhere colleges, dentists,
supermarkets, banks, DVD stores, hospitals,
hotels, gyms, - there are many more examples.
Within each of these organisations the following
information could be store; customers, sales,
products, suppliers, purchasers, Stock,
accounts, VAT.
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These databases are organised in such a
way that data can be easily entered,
stored, edited, deleted and manipulated
to support the activities of the
organisation.
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Advantages
Easy to use
records are easy to access and retrieve
data can easily be manipulated in many
ways
data can be validated to ensure that it is
accurate when input
easy to store
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Disadvantages
Database structures must be carefully
developed to ensure that they work as
efficiently as possible
there are laws that control the use of databases
many people feel that simply too much
information is stored about us
the cost of technology can be prohibitive
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Data Types
Just as with software development understanding data
types is an important part of being able to work
successfully with databases.
 Text - allows you to hold alphanumeric data. Means can
hold numbers and characters, combinations give
examples mention the default numbers that are set and
the numbers that can be adjusted to.
 Number- whole numbers, decimals ect
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Data Types
 Currency- As with number need to choose correct settings
 Date/Time- Recognizes formats give examples short
medium dates
 AutoNumber- a number the computer automatically
generates. Example what it does?
 LookupWizard- able to set up values that are stored in
advance user can make a choice from a list - give examples
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Terminology
An object is something that can be designed,
selected and manipulated Tables, queries,
forms and reports are all examples of objects.
Tables consists of rows and columns, where
the row contains a record and the column
becomes a record field.
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Database Structures
 Tables are the foundation to a database - Most
databases contain number of tables they store different
information. Give examples of information .
 Fields are the columns in the table. Each column has a
field heading basically a name give example.. All the
data in the field will be of the same type example…. And
related give examples….
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Database Structures
Record - a record is a single piece of
information with all the relevant parts give
an example of a complete single record.
Each record is stored in a row.
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Database Structures
 Primary Key - Each record that is stored must have
something completely unique about it. This is so the
records that are similar can be told apart.
 Usually a field is selected which will contain a unique
piece of data.
 This is then allocated a primary key give examples of
unsuitable and suitable field names with simple reasons
why
 ID is created, often using the Auto Number give reasons
why?
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Forms
To enable users to use databases more
easily, the data in tables is often [in fact
usually] accessed through a form
the form changes the way the user
accesses and uses the records.
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Query structure
Used to interrogate the data in a database.
This means filtering and sorting the data to
answer questions.
The query uses the data in the table, by
searching the information in the fields and
applying the chosen criteria.
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Sorting records
You can sort data via the query in design
view.
You can also sort data directly in the
table.
Simply click on the relevant field and one
of the sorting icons. A to[ascending
order] or Z to A [descending order]
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Reports
A report is a printed record of data in the
database.
There are several benefits of presenting
information in a report rather than just
viewing the data on-screen.
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Layouts
 Columnar layout- each record is laid out with the
fields underneath each other. The labels are placed to
the left of the data. This layout ideal when there is a lot
of data in each record.
 Tabular layout - this arranges the data in a table can
be used for forms and reports if the amount of data in
each record fits comfortably.
 Justified layout- this displays data one record at a
time. The appearance is a formal boxed style. Which
fits neatly across the page, with the labels for each field
above the data. It makes efficient use of space.
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D1 - Reports
It counts the records in the report and displays
the result.
it adds a heading that can be changed by the
user.
It adds the date and time.
It adds a age number
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Reports – D2
 Reports are very useful if you wish to share some of the
information in the database with others in a printed format.
 Reports can be laid out so they are easy to read and
understand
 Reports can be used to select and present exactly the data
that someone needs rather than everything in the database.
 Although reports are intended to be printed as hard copy,
they can also be transferred as electronic documents by
email.
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