Databases and Database Management Systems

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

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

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

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

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

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

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

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

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

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

COLLEGE DATABASE Databases and DBMS

COLLEGE DATABASE Databases and DBMS

COLLEGE DATABASE Databases and DBMS

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

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

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

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

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

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

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

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

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

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

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