Database basics

Revise Database basics for Information Technology 9626 (AS Level) — revision notes, 121 practice questions and instant AI marking.

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10.1 · Chapter 10 · AS Level IT · Hodder Education

Database Basics

Flat-file vs relational databases, data types, relationships, key fields, ERDs, designing and creating a database in Access, querying, forms, and switchboards.

📋 Database Types

🔑 Key Fields

📊 ERDs

🔍 Queries

📝 Forms & Switchboards

The Big Idea: A relational database stores data in multiple linked tables to avoid repetition. Understanding how tables link (via key fields), how to design the structure (using ERDs), and how to query and present the data professionally is the core of this entire chapter.

10.1.1Database Types

📄 Flat-File Database

Stores all data in one table organised by rows (records) and columns (fields). Simple to create but leads to massive data duplication when relationships exist between entities. Every teacher-student combination requires a full row even if the teacher data is identical.

🔗 Relational Database

Stores data in two or more linked tables. Same data is not stored multiple times. Each table has a primary key. Tables are linked via foreign keys. Fewer data entry errors, less storage, faster searches, easier updates and deletions.

Feature	Flat-File	Relational
Number of tables	1	2 or more
Data duplication	High (lots of redundant data)	Minimal (stored once)
When to use	One dataset, few repeated items	Multiple linked datasets
Editing data	Must update every occurrence	Change once in one table
Storage	More — repeated data	Less — no redundancy
Search speed	Slower (more data to search)	Generally faster (indexed fields)

10.1.2Data Types

Data Type	Access Name	Stores	Important Notes
Alphanumeric	Short Text / Long Text	Letters, numbers NOT used for calculations (phone numbers, postcodes)	Use for any text including numbers that won't be calculated
Integer	Number (Integer/Long Integer)	Whole numbers used for calculations	Use Long Integer for 3+ digits. NEVER store phone numbers as numbers
Decimal	Number (Double/Single)	Numbers with decimal places	Set decimal places in field properties
Currency	Currency	Monetary values with currency formatting	Currency symbol is for display only — not stored (saves space)
Date/Time	Date/Time	Dates and/or times as a number	Set format in field properties (Short Date, Short Time, etc.)
Boolean/Logical	Yes/No	Yes/No, True/False, or 0/-1 values	Format to Yes/No, True/False, or On/Off
AutoNumber	AutoNumber	Automatically generated unique numbers	Useful for automatic primary keys
Attachment / OLE	Attachment / OLE Object	Images, documents, spreadsheets, audio, video	Used in web-facing applications with back-end databases

⚠️ Key exam rule: Only use a numeric field type if the data will be used in a calculation. Telephone numbers, postcodes, ID numbers — all stored as alphanumeric (text), even though they look like numbers.

10.1.3Relationship Types

Type	Symbol in ERD	Definition	Example
One-to-One (1:1)	Single line \| at each end	Each record in table A relates to exactly ONE record in table B. Linked fields in both tables must contain the same unique values.	One driver has one driving licence
One-to-Many (1:∞)	Single line \| at "one" end, crow's feet at "many" end	Each record in table A can relate to MANY records in table B. Primary key in one table links to foreign key in another.
Many-to-Many (∞:∞)

10.1.4Key Fields

🔑 Primary Key

unique data

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📋 Summary & Review
✅ Concepts Checklist
🧠 What to Memorise
🎯 Exam Tips

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Database basics

Database Basics

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