Chapter 9: Database - Study Notes for OL IT Students

🎯 Learning Objectives

✓ Definition of database
✓ Advantages of using a database
✓ Special characteristics of a database
✓ Using fields to create tables
✓ Identifying key fields
✓ Relational databases
✓ Relationships between tables
✓ Using queries to get data
✓ Using data forms
✓ Using reports to furnish information

9.1 Database Concept

Database: A collection of organized data that can be efficiently stored, retrieved, and managed.

Types of Databases

1. Manual Database: Data written and stored on paper (e.g., phone book)

2. Electronic Database: Data stored on electronic medium (e.g., computer, mobile phone)

📱 Real-World Example: Phone Book

A phone book is a simple database where:

Names are organized alphabetically
Each contact has a name and phone number
Information can be quickly retrieved when needed

Figure 9.1 - Manual Phone Book

Figure 9.2 - Electronic Phone Book

9.1.1 Advantages of Databases

More efficient in retrieving information: Data is properly organized in tables, making it quick to find required information.
Easy to obtain copies: Electronic databases can be copied very easily.
Smaller physical space: Electronic databases require much less physical space compared to manual databases.
Efficient data analysis: Only necessary data can be selected and processed.
Data can be shared: The same database can be used in different application software.
Independence of data: Database tables can be updated without changes to the application software.

9.1.2 Features of a Database

Minimal data redundancy: Reduces storing the same data in multiple places.
Data consistency: Ensures the same data across different tables is accurate and uniform.
Increases efficiency: Properly organized tables make saving and reading data faster.
Increases accuracy: Minimizing redundancy maintains data consistency and accuracy.
Increases validity: Field properties ensure data entered meets specific criteria.
Security: Unauthorized access can be controlled using passwords and encryption.

🔍 Example: Data Redundancy Problem

Problem: If student name "Firosa Lai" is stored in both admission table and library table, changing it to "Firosa Rafeeq" requires updating both tables.

**Table 9.1 - Admission Table (Before)**
Student Number	Name	Date of Birth	Date of Admission
100	Manoj Dayarathne	2/9/2008	1/1/2014
101	Firosa Lai	4/2/2008	1/1/2014

Solution: Use relational database with primary and foreign keys to store name only once.

📝 Important Note: Data encryption translates data in such a way that unauthorized personnel cannot read it, increasing security.

Figure 9.4 - Data Encryption

9.1.3 Electronic and Manual Databases

**Table 9.4 - Comparison of Manual and Electronic Databases**
Manual Database	Electronic Database
Less efficient	More efficient
Less accurate	More accurate
Less credible	More credible
Difficult to analyze data	Easy to analyze data
Must present in order of input	Can change data input order
Difficult to delete unnecessary data	Easy to delete unnecessary data
Difficult to update data	Easy to update data
More space needed	Very small space needed
More manpower needed	Less manpower needed

9.1.4 Introduction to Relational Database

Field: A single piece of information (a column in a table)

Record: A collection of fields related to one person or object (a row in a table)

Data Table: A collection of records

Relational Database: A collection of related tables

Database Structure Hierarchy:

Field 1 + Field 2 + Field 3 + ... = Record

Record 1 + Record 2 + Record 3 + ... = Table

Table 1 + Table 2 + Table 3 + ... = Relational Database

Figure 9.5 - Relational Database Structure

📚 Example: Student Records

**Table 9.6 - Student Records**
Admission No	Name	Date of Birth	Gender	Telephone No
1426	Kavindu Prabashwara	2005.05.23	Male	0352287571
1427	Meenadevi Ramanathan	2005.08.12	Female	0352235696
1428	Mohommad Malikkar	2005.02.07	Male	0352815402

In this table:

Each column represents a field
Each row represents a record
There are 5 fields and 3 records

9.1.5 Primary Key

Primary Key: A column (or combination of columns) that uniquely identifies each record in a table.

Special Attributes of a Primary Key:

Should not be empty (mandatory)
No duplicate values (must be unique)
Usually underlined in table design

📖 Example: Book Table

**Table 9.7 - Book Table**
Accession No	Title	Author's Name	Price	Number of Books
2131	Let's Access Internet	Mahesh Gankanda	Rs. 275.00	10
2132	Computer Studies	Suranimala Basnayaka	Rs. 300.00	5
2133	Essay Writing	Nimali Bogoda	Rs. 225.00	12

Analysis:

✓ Accession No: Unique for each book - Best for Primary Key
✗ Title: Can have duplicates (same book name by different authors)
✗ Author's Name: One author can write multiple books
✗ Price: Different books can have same price
✗ Number of Books: Multiple books can have same quantity

🔑 Common Primary Key Examples:

National Identity Card Number
School Admission Number
Employee ID
Product Code
Customer ID

9.1.6 Composite Primary Key

Composite Primary Key: A primary key that consists of two or more columns to uniquely identify a record.

⚽ Example: Sports Table

**Table 9.9 - Sports Table**
Year	Sport	Captain	Vice Captain
2013	Cricket	Rashmi Senarathne	Mubharak Husein
2013	Football	Jaliya Saranga	Vinothen Raj
2014	Cricket	Mubharak Husein	Bhanu Dayarathne
2014	Football	Jaliya Saranga	Ahammed Nawas

Why Composite Key?

Year alone: Has duplicates (2013, 2014)
Sport alone: Has duplicates (Cricket, Football)
Year + Sport together: Unique combination!

Composite Primary Key = Year + Sport

9.1.7 Foreign Key

Foreign Key: A field (or combination of fields) in one table that refers to the primary key in another table, creating a relationship between the tables.

Special Features of a Foreign Key:

Builds a connection between two tables
The related data of the primary key field exists in the other table
Foreign key of one table is the primary key of another table

🔗 Example: Student and Subject Tables

**Table 9.11 - Student Table**
Registration Number	Name	Date of Birth	Date of Admission
100	Manoj Dayarathne	2/9/2014	1/1/2014
101	Firosa Rafeeq	4/2/2014	1/1/2014

**Table 9.12 - Subject Table**
Candidate No	Maths	Science	Sinhala	English	Registration No
449683	B	A	C	C	100
449697	A	B	B	A	101

In this example:

Registration Number is the Primary Key of Student Table
Registration Number is the Foreign Key of Subject Table
Candidate No is the Primary Key of Subject Table

Figure 9.6 - Primary Key and Foreign Key Relationship

Disadvantages of Data Duplication

⚠️ Problems with Data Duplication:

Inability to select a primary key field: Duplicate data makes it difficult to maintain record identity.
Inability to analyze data properly: Same student counted multiple times leads to incorrect analysis.
Reduced efficiency: More time spent entering the same data repeatedly.
High possibility of inaccurate data: Errors can occur when entering same data multiple times (e.g., "Malikkar" vs "Malakkar").
Difficult to input data: Must enter name, date of birth repeatedly for each record.
Errors in deleting data: Multiple records for one student can lead to deletion mistakes.
Difficult to update data: Must update each duplicate record separately.

✅ Solution: Split into Related Tables

**Table 9.15 - Student Table**
Admission No	Name	Date of Birth
1426	Kavindu Prabashwara	2005.05.23
1427	Meenadevi Ramanathan	2005.08.12
1428	Mohommad Malikkar	2005.02.07

**Table 9.16 - Marks Table**
Admission No	Marks	Term	Year
1426	69	1	2014
1427	82	1	2014
1426	79	2	2014

Benefits:

✓ Student information stored only once
✓ No data duplication
✓ Easier to update student details
✓ Clear primary key (Admission No in Student Table)
✓ Foreign key (Admission No) links the tables

9.2 Data Types

Data Type: A type of data related to one field that determines what kind of data can be stored and how it can be used.

Common Data Types:

Data Type	Description	Examples
Numeric	Used for calculations
• Integer	Whole numbers (positive or negative)	12, -23, 0
• Real	Numbers with decimal places	8.125, -2.64, 4.00
Text	Letters, numbers, or special characters (not for calculations)	889534731V, 0112785123
Currency	Monetary values	$12.45, Rs. 35.00
Date/Time	Dates and times	12/23/2013, 7:35 AM
Boolean	Logical values only	True, False

💡 Important: Although telephone numbers contain digits, they should be stored as Text data type because:

They are not used for calculations
They may contain special characters (e.g., 0112-985123)
Leading zeros must be preserved (e.g., 0352287571)

📝 Example: Choosing Data Types

**Table 9.17 - Field Data Types**
Field	Data Type	Reason
Admission Number	Text	Not used for calculations, may have letters
Date of Admission	Date/Time	Stores date information
Subject Code	Text	Alphanumeric identifier
Doctor's Fee	Currency	Monetary value
Department Name	Text	Textual information
Number of Passengers	Integer	Whole number for counting
Is Registered?	Boolean	Yes/No or True/False value

9.4 Creating a Relational Database

9.4.1 Types of Relationships

1. One-to-One Relationship (1:1)

A relationship where one record in Table A relates to only one record in Table B, and vice versa.

Example: Student and Scholarship Marks

Figure 9.11 - One-to-One Relationship Diagram

Characteristics:

Each student has exactly one scholarship exam record
Each scholarship record belongs to exactly one student
Primary Key: Admission No (Student Table), Index No (Marks Table)
Foreign Key: Admission No in Marks Table

2. One-to-Many Relationship (1:M)

A relationship where one record in Table A can relate to multiple records in Table B, but each record in Table B relates to only one record in Table A.

Example: Student and Fee Payments

Figure 9.12 - One-to-Many Relationship Diagram

Characteristics:

One student can make multiple fee payments
Each payment belongs to exactly one student
Primary Key: Admission No (Student Table), Receipt No (Fees Table)
Foreign Key: Admission No in Fees Table

**Features of One-to-Many Relationship**
Table A (Parent)	Table B (Child/Related)
One record can relate to multiple records in Table B	Each record relates to only one record in Table A
Can have records not related to Table B	Cannot have records not related to Table A
Primary key data cannot duplicate	Foreign key data can duplicate

3. Many-to-Many Relationship (M:N)

A relationship where multiple records in Table A can relate to multiple records in Table B, and vice versa. This requires a junction table to implement.

Example: Students and Sports

Figure 9.13 - Many-to-Many Relationship Converted to Two One-to-Many

Characteristics:

One student can participate in multiple sports
One sport can have multiple students
Requires a junction table (Students Sports Table)
Composite Primary Key in junction table: Admission No + Sport No

**Student Table**
Admission No	Name	Date of Birth
1426	Kavindu Prabashwara	2005.05.23
1428	Mohommad Malikkar	2005.02.07

**Students Sports Table (Junction Table)**
Admission No	Sport No	Team
1426	S001	A
1426	S002	A
1428	S001	B

**Sports Table**
Sport No	Sport	Number of Members
S001	Cricket	11
S002	Football	16

🖥️ 10 Practical Examples with Microsoft Access

Example 1: Creating a Simple Library Database

Steps:

Open Microsoft Access
Create → Table Design
Add fields:
- Accession_No (Text) - Primary Key
- Book_Title (Text)
- Author_Name (Text)
- Price (Currency)
- Quantity (Number)
Right-click Accession_No row → Primary Key
Save table as "Books"

Library Table in Design View

Example 2: Student Registration System

Create Student Table:

Field Name	Data Type	Properties
Student_ID	Text	Primary Key, Field Size: 10
Full_Name	Text	Field Size: 50
Date_of_Birth	Date/Time	Format: Short Date
Email	Text	Field Size: 50
Phone_Number	Text	Field Size: 15

Student Registration Table

Example 3: Creating a One-to-Many Relationship

Tables: Customer and Orders

Customer Table:

Customer_ID (Text) - Primary Key
Customer_Name (Text)
City (Text)

Orders Table:

Order_ID (Text) - Primary Key
Order_Date (Date/Time)
Amount (Currency)
Customer_ID (Text) - Foreign Key

Creating Relationship:

Database Tools → Relationships
Add both tables
Drag Customer_ID from Customer table to Customer_ID in Orders table
Check "Enforce Referential Integrity"
Check "Cascade Update Related Fields"
Check "Cascade Delete Related Records"
Click Create

Customer-Orders Relationship

Example 4: Product Inventory Database

Product Table Fields:

Field Name	Data Type	Description
Product_Code	Text	Primary Key (e.g., "PROD001")
Product_Name	Text	Name of the product
Category	Text	Product category
Unit_Price	Currency	Price per unit
Stock_Quantity	Number (Integer)	Available quantity
Reorder_Level	Number (Integer)	Minimum stock level

Product Inventory System

Example 5: Creating a Query to Filter Data

Task: Find all books with price less than Rs. 300

Steps:

Create → Query Design
Add the "Books" table
Select fields: Accession_No, Book_Title, Author_Name, Price
In the "Criteria" row under Price, type: <300
Run the query

Query to Filter Books by Price

Example 6: Creating a Form for Data Entry

Task: Create a user-friendly form for entering student data

Steps:

Select the Student table
Create → Form
Access automatically creates a form
Switch to Design View to customize
Add a title label "Student Registration Form"
Save the form

Student Data Entry Form

Example 7: Creating a Report for Printing

Task: Create a report showing all students sorted by name

Steps:

Create → Report Wizard
Select Student table
Add fields: Student_ID, Full_Name, Date_of_Birth, Email
Sort by: Full_Name (Ascending)
Choose layout: Tabular
Give title: "Student Directory"
Finish

Student Directory Report

Example 8: Query with Calculations

Task: Calculate total inventory value (Unit_Price × Stock_Quantity)

Steps:

Create → Query Design
Add Product table
Add fields: Product_Code, Product_Name, Unit_Price, Stock_Quantity
In a new column, type: Total_Value: [Unit_Price]*[Stock_Quantity]
Run the query

Inventory Value Calculation Query

Example 9: Using Parameter Query

Task: Search for students by entering their name

Steps:

Create → Query Design
Add Student table
Select all fields
In Criteria row under Full_Name, type: [Enter Student Name:]
Run the query - a dialog box will appear
Enter a name to search

Parameter Query for Student Search

Example 10: Many-to-Many Relationship Implementation

Task: Create a system where students can enroll in multiple courses and courses can have multiple students

Table 1: Students

Student_ID (Primary Key)
Student_Name

Table 2: Courses

Course_ID (Primary Key)
Course_Name

Table 3: Enrollments (Junction Table)

Enrollment_ID (Primary Key)
Student_ID (Foreign Key)
Course_ID (Foreign Key)
Enrollment_Date

Creating Relationships:

Create two one-to-many relationships:
- Students to Enrollments (Student_ID)
- Courses to Enrollments (Course_ID)
Enforce referential integrity for both

Student-Course Enrollment System

📝 10 Practical Activities

Activity 1: Create a Personal Contact Database

Task: Create a database to store contact information of your friends and family.

Requirements:

Create a table with fields: Contact_ID, Name, Phone, Email, Birthday
Set appropriate data types
Define primary key
Enter at least 10 contacts

Activity 2: School Library System

Task: Design a complete library management system.

Requirements:

Create three tables: Books, Members, Borrowing
Establish proper relationships
Create a query to show borrowed books
Design a form for book borrowing

Activity 3: Restaurant Menu Database

Task: Create a database for a restaurant menu.

Requirements:

Fields: Item_Code, Item_Name, Category, Price, Available
Create a query to show items by category
Create a report showing the complete menu

Activity 4: School Event Management

Task: Design a database to manage school events and participants.

Requirements:

Create tables: Events, Students, Participation
Implement many-to-many relationship
Create query to show event participants

Activity 5: Marks Management System

Task: Create a database to store student marks for different subjects.

Requirements:

Tables: Students, Subjects, Marks
Create a query to calculate average marks
Generate a report card

Activity 6: Hospital Appointment System

Task: Design a simple appointment booking system.

Requirements:

Tables: Patients, Doctors, Appointments
Include fields for appointment date and time
Create query to show daily appointments

Activity 7: Online Store Database

Task: Create a database for an online store.

Requirements:

Tables: Products, Customers, Orders, Order_Details
Establish all necessary relationships
Create query to calculate total sales

Activity 8: Movie Collection Database

Task: Manage your personal movie collection.

Requirements:

Fields: Movie_ID, Title, Genre, Year, Rating, Watched
Create query to filter by genre
Create form for adding new movies

Activity 9: Sports Club Management

Task: Create a database for a sports club.

Requirements:

Tables: Members, Sports, Participation
Track membership fees and payment dates
Create report showing active members

Activity 10: Classroom Attendance Tracker

Task: Design a database to track student attendance.

Requirements:

Tables: Students, Attendance_Records
Fields for date, present/absent status
Create query to calculate attendance percentage
Generate monthly attendance report

❓ 20 Questions & Answers

Q1. What is a database? Define with an example.

Answer: A database is a collection of organized data that can be efficiently stored, retrieved, and managed.

Example: A phone book that contains names and phone numbers organized alphabetically is a simple database. The electronic version stored in a mobile phone is an electronic database where contacts can be quickly searched and retrieved.

Q2. List and explain five advantages of using electronic databases over manual databases.

Answer:

More efficient in retrieving information: Data organized in tables can be searched and found very quickly.
Easy to obtain copies: Electronic databases can be backed up and copied easily.
Smaller physical space: Large amounts of data can be stored on small electronic devices.
Efficient data analysis: Specific data can be selected and processed for analysis.
Data independence: Database structure can be changed without affecting application software.

Q3. What is data redundancy? Explain with an example why it should be minimized.

Answer: Data redundancy occurs when the same data is stored in multiple places in a database.

Example: If a student's name "Firosa Lai" is stored in both the admission table and library table, changing it to "Firosa Rafeeq" requires updating both tables. This:

Wastes storage space
Increases chances of errors
Reduces efficiency
Can lead to data inconsistency if one instance is updated but another is missed

Q4. Define the following terms: Field, Record, and Table with examples.

Answer:

Field: A single piece of information (a column in a table). Example: "Student_Name", "Date_of_Birth"
Record: A collection of related fields for one entity (a row in a table). Example: One student's complete information including name, ID, birth date, etc.
Table: A collection of records organized in rows and columns. Example: A "Students" table containing records of all students with their details.

Q5. What is a Primary Key? What are its special characteristics?

Answer: A Primary Key is a column (or combination of columns) that uniquely identifies each record in a table.

Special Characteristics:

Cannot be empty: Must always have a value (mandatory)
Must be unique: No duplicate values allowed
Unchanging: Should not change frequently

Examples: National ID Number, School Admission Number, Employee ID

Q6. Explain Composite Primary Key with an example.

Answer: A Composite Primary Key is a primary key made up of two or more columns that together uniquely identify a record.

Example: In a Sports Captain table:

Year alone has duplicates (2013, 2013, 2014, 2014)
Sport alone has duplicates (Cricket, Cricket, Football, Football)
But Year + Sport combination is unique (2013-Cricket, 2013-Football, 2014-Cricket, 2014-Football)

Therefore, Composite Primary Key = Year + Sport

Q7. What is a Foreign Key? How does it create relationships between tables?

Answer: A Foreign Key is a field (or combination of fields) in one table that refers to the Primary Key in another table.

How it creates relationships:

Links two tables together
The Foreign Key in one table matches the Primary Key in another table
Maintains referential integrity
Enables data retrieval from multiple related tables

Example: Student_ID is the Primary Key in the Students table and Foreign Key in the Marks table, creating a relationship between them.

Q8. Why should telephone numbers be stored as Text data type instead of Number data type?

Answer: Telephone numbers should be stored as Text because:

Not used for calculations: We never add, subtract, or perform mathematical operations on phone numbers
Leading zeros: Numbers like 0352287571 would lose the leading zero if stored as Number (becoming 352287571)
Special characters: Phone numbers may contain hyphens, spaces, or parentheses (e.g., 0112-985123, (011) 2345678)
International format: May include plus signs and country codes (e.g., +94 11 2345678)

Q9. List and explain the common data types used in databases.

Answer:

Text: Stores letters, numbers, and special characters. Not for calculations. Example: Names, addresses, ID numbers
Number (Integer): Stores whole numbers. Example: Age, quantity, count
Number (Real/Decimal): Stores numbers with decimal places. Example: Height, weight, percentages
Currency: Stores monetary values. Example: Prices, salaries, fees
Date/Time: Stores dates and times. Example: Birth date, appointment time
Boolean (Yes/No): Stores only True/False values. Example: Registered?, Active?, Passed?

Q10. Explain the three types of relationships in relational databases with examples.

Answer:

One-to-One (1:1): One record in Table A relates to only one record in Table B.
Example: One student has one scholarship exam record; one exam record belongs to one student.
One-to-Many (1:M): One record in Table A relates to multiple records in Table B.
Example: One student can make multiple fee payments; each payment belongs to one student.
Many-to-Many (M:N): Multiple records in Table A relate to multiple records in Table B.
Example: One student can enroll in multiple courses; one course can have multiple students. Requires a junction table.

Q11. What is data encryption? Why is it important for database security?

Answer: Data encryption is the process of translating data into a coded format that unauthorized personnel cannot read or understand.

Importance:

Protects sensitive information: Personal details, passwords, financial data remain secure
Prevents unauthorized access: Even if someone gains access to the database file, they cannot read encrypted data
Maintains confidentiality: Ensures privacy of individuals whose data is stored
Compliance: Meets legal and regulatory requirements for data protection

Q12. List and explain five disadvantages of data duplication.

Answer:

Inability to maintain record identity: Cannot select a proper primary key field when data is duplicated
Incorrect data analysis: Same person counted multiple times leads to wrong statistics
Reduced efficiency: More time spent entering the same data repeatedly
Increased inaccuracy: Spelling errors (e.g., "Malikkar" vs "Malakkar") can occur when entering same data multiple times
Difficult to update: Must update every duplicate instance, increasing chance of missing some

Q13. What is a relational database? How is it structured?

Answer: A relational database is a collection of related tables that are connected through primary and foreign keys.

Structure:

Fields: Individual data items (columns)
Records: Collection of fields (rows)
Tables: Collection of records
Relationships: Connections between tables using keys

Hierarchy: Fields → Records → Tables → Relational Database

Q14. Explain the concept of referential integrity in databases.

Answer: Referential integrity is a database rule that ensures relationships between tables remain consistent.

Key Principles:

Cannot add records: Cannot add a record in the related table with a foreign key value that doesn't exist in the primary table
Cannot delete records: Cannot delete a record from the primary table if related records exist in the related table
Cascade updates: When a primary key value is updated, all related foreign key values are automatically updated
Cascade deletes: When a record is deleted from the primary table, all related records in the related table are automatically deleted

Q15. What is a Database Management System (DBMS)? Name three examples.

Answer: A Database Management System (DBMS) is a collection of programs that enables users to create, maintain, and manage databases efficiently.

Components/Objects of DBMS:

Tables
Queries
Forms
Reports

Examples:

Microsoft Access - by Microsoft Corporation
LibreOffice Base - by The Document Foundation
Oracle Database - by Oracle Corporation

Q16. What is a query? Why is it used in databases?

Answer: A query is a request for specific information from one or more database tables.

Uses of Queries:

Filter data: Display only records that meet certain criteria (e.g., students scoring above 60 marks)
Sort data: Arrange records in ascending or descending order
Calculate data: Perform calculations like totals, averages, counts
Combine data: Retrieve data from multiple related tables
Update data: Modify multiple records at once

Example: A query to find all books in the library with price less than Rs. 300.

Q17. What is the purpose of a form in a database?

Answer: A form provides a user-friendly interface for entering, viewing, and editing data in a database.

Purposes:

Easy data entry: Presents fields in a clear, organized layout rather than a spreadsheet-like view
Data validation: Can include validation rules to ensure correct data entry
User-friendly: Makes database accessible to non-technical users
Control access: Can limit which fields users can see or edit
Navigation: Provides buttons and controls to move between records

Example: A student registration form showing one student's details at a time with clear labels and input boxes.

Q18. What is a report? How is it different from a query?

Answer: A report is a formatted presentation of database information designed for printing or viewing.

Differences from Query:

Query	Report
Used to retrieve data	Used to present data
Data can be edited	Data cannot be edited
Basic formatting	Professional formatting with headers, footers, grouping
Not designed for printing	Optimized for printing
Can perform calculations	Can display calculated totals, subtotals, summaries

Q19. How do you implement a Many-to-Many relationship in a database?

Answer: A Many-to-Many relationship is implemented using a junction table (also called bridge table or linking table).

Steps:

Create the two main tables (e.g., Students and Sports)
Create a junction table (e.g., Students_Sports)
Include foreign keys from both main tables in the junction table
The composite primary key of the junction table consists of both foreign keys
Create two one-to-many relationships:
- Students to Students_Sports (one-to-many)
- Sports to Students_Sports (one-to-many)

Result: The many-to-many relationship is converted into two one-to-many relationships.

Q20. Compare and contrast manual and electronic databases (list at least 5 differences).

Answer:

Aspect	Manual Database	Electronic Database
Efficiency	Less efficient - slow to find information	More efficient - quick searches
Accuracy	Less accurate - prone to human error	More accurate - validation rules prevent errors
Storage Space	Requires large physical space	Requires minimal physical space
Data Updates	Difficult to update - manual corrections	Easy to update - quick modifications
Data Analysis	Difficult to analyze - manual calculations	Easy to analyze - automatic calculations
Backup	Difficult - must photocopy everything	Easy - simple file copying
Manpower	More manpower needed	Less manpower needed

📚 Chapter Summary

Database: A collection of organized data that can be efficiently stored, retrieved, and managed.
Field: A column in a table (single piece of information)
Record: A row in a table (collection of related fields)
Table: A collection of records
Relational Database: A collection of related tables connected through keys
Primary Key: A unique identifier for each record; cannot be empty or duplicate
Composite Primary Key: A primary key made of two or more fields
Foreign Key: A field that links to the primary key of another table
Data Redundancy: Storing the same data in multiple places (should be minimized)
Data Consistency: Ensuring data accuracy across all tables
Data Types: Text, Number (Integer/Real), Currency, Date/Time, Boolean
Relationships: One-to-One, One-to-Many, Many-to-Many
DBMS Objects: Tables, Queries, Forms, Reports
Query: Used to retrieve and analyze specific data from tables
Form: User-friendly interface for data entry and viewing
Report: Formatted presentation of data for printing
Referential Integrity: Ensures relationships between tables remain consistent
Data Encryption: Protects data by converting it to unreadable format
Advantages of Electronic Databases: Efficient, accurate, space-saving, easy to analyze and share
Junction Table: Used to implement many-to-many relationships

🎯 Key Points to Remember for Exams:

Always underline primary keys in table designs
Choose appropriate data types for each field
Telephone numbers should be Text, not Number
Minimize data redundancy to maintain consistency
Foreign keys create relationships between tables
Many-to-many relationships require a junction table
Queries can filter, sort, and calculate data
Forms are for data entry, Reports are for presentation