Transcript Relational Databases

Relational Database Management
System (RDBMS) – MS Access
Database Management System (DBMS)
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A set of programs that permits an organisation to:
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Using a DBMS, users can
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create new database files
add, delete, alter, and sort data
make enquiries and print reports
The DBMS will
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centralise data
create database files
manage them efficiently
access the data when required
allow many users to simultaneously access the central database
restrict access for each user to those parts of the database that they are entitled
to view or change
MS Access has many of the features of a DBMS.
Basic Components
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Tables
Forms
Queries
Reports
Tables
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A table for each separate entity
Design mode allows user to define a data
structure for the table
A primary key – which must be a unique
identifier for each record - must be defined.
(Access does provide an Autonumber
function is there is no natural unique
identifier.
Forms
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A user-friendly method of entering data for the main
user(s) of a database
Usually has one data source, which may be a table
or a query
The objects that allow fields to displayed and/or
modified are known as controls
Design is very important
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Order of controls
Layout of controls
Queries
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Used to create subsets of data held in tables
Used to combine the contents of more than one table
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This is achieved via the relational links that are created
between tables
The are several types of query
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Simple select query
Update query
Append query
Delete query
Crosstab query
Reports
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Reports are usually used in conjunction with
queries to produce sorted output satisfying
particular criteria
MS Access provides powerful wizards to
produce reports with various sort, grouping and
style options.
Relationships
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The relational database model depends upon the creation of
relational links between separate entities (tables)
One-to-Many relationship
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For example in a surgery database, a doctor would have many patients
Doctors
Patients
 One-to-one relationship
– a doctor would have one expense account
Doctors
Expenses