1. Databases and Database Management Systems

2. Definition
A database is an application package used for storage and retrieval of data
A database is a structured collection of related data
Databases and DBMS

3. Why Use a Database?
All organisations need to keep records of transactions they perform with suppliers and customers
Organisations need records of employees, orders, invoices etc
The business needs to be able to find information quickly and easily as needed
Databases and DBMS

4. Terminology
Entity
This is the thing/object you are recording information about.
Types of entities
Person Employee
Country Customer
Product Invoice
Order Part
Databases and DBMS

5. Attributes
Attributes are the characteristics that describe the entities. For the entity Employee:
Name - Address
Age - Gender
Tel No - Soc Sec Number etc
Dept - Date Hired
Databases and DBMS

6. Fields This is where we store the attributes
Name
Age
Address etc
No two fields can have the same name
Databases and DBMS

7. Record
A record holds all the data relating to a single person or a single transaction etc
A record is a collection of Fields
The number if Fields needed depends on the subject
Databases and DBMS

8. A File Is a collection of records
All the student records would make up the Student File
All the employee’s records could make up the Employee File
Databases and DBMS

9. A Organisation Database
Contains all the files within the organisation
A College Database could contain the following files
Student File
Course File
Grant File
Personnel File
Student Applications File
Databases and DBMS

10. Database Models
Not all databases store data in the same way. This depends on the type of software used.
Database Models are
Relational - Hierarchical
Network - Object Oriented
For our course we are using Access which is a Relational Model
Databases and DBMS

11. DBMS
The Database Management System (DBMS) is the software that manages the database
It is the user interface that allows the user to create, add, delete and generally manipulate the data in the database
Databases and DBMS

12. COLLEGE DATABASE
Databases and DBMS

13. COLLEGE DATABASE
Databases and DBMS

14. COLLEGE DATABASE
Databases and DBMS

15. Linking We need to repeat some fields so that we can LINK the tables
The repeated fields allow us to link the information in one table to that in another
Databases and DBMS

16. PRIMARY KEY A primary key is one that uniquely identifies a record
Student ID is a number allocated to each student as there may be 2 students with the same name
Databases and DBMS

17. Relationships
If we want to link data from different tables we must define RELATIONSHIPS between the tables
This involves linking the Primary Key field of one table with a field in a second table
Databases and DBMS

18. Database Query
When we want to extract information from a database this is called a ‘Query’
The result is a screen display that shows the information you want which may have been extracted for one or more tables
Databases and DBMS

19. Features of a DBMS It allows us to create database files
It enables the user to update, delete, add or change data in the database
It enables the user to link tables
It enables the user to query the database
The user can produce reports on screen or in printed form
Databases and DBMS

20. Query “Co Mayo”
If we query the Student database regarding which students come from Co Mayo the database will give us the following result
Databases and DBMS

21. Advantages of Databases
The DBMS makes the entry of data to the system is quick and easy
Data is organised in a way that minimises data redundancy (re-entering of the same data over and over)
Databases and DBMS

22. Advantages
A DBMS allows the organisation to have a central store of information so anyone who needs access can get it
A DBMS can keep data secure by using passwords etc and limiting access to the data
Better access to data for decision-making
Databases and DBMS

23. Advantages Easy update and retrieval of data
Easy to create reports for management
Reduced data redundancy
Data is shared throughout the organisation
Better security of data
Better data integrity
Databases and DBMS

24. Disadvantages Cost of the software Complexity
Size – huge amounts of data
Backup procedures required
High impact of failure
Skilled personnel needed to maintain a DBMS
Databases and DBMS

25. Summary A DBMS is a powerful piece of software for managing data
Can store large quantities of data
Data is consistent throughout the organisation when a DBMS is used (data integrity)
It is easier to maintain data security
It is much easier to distribute information throughout the organisation
Databases and DBMS