Topic 3 of 7Aga Khan Board

Data & Databases

Data types, file storage, databases and SQL basics

Data is raw facts and figures. Information is processed, meaningful data.

Data types:

Integer: whole numbers (e.g., age = 17)

Real/Float: decimal numbers (e.g., price = 149.99)

Character: single symbol (e.g., 'A')

String: sequence of characters (e.g., "Muhammad Ali")

Boolean: True or False (e.g., is_passed = True)

Date/Time: e.g., 25/03/2026

File storage concepts:

Record: one complete entry (e.g., one student's data)

Field: one item within a record (e.g., student name)

Key field: unique identifier for each record (e.g., student ID)

Databases store data in organised tables (like a structured spreadsheet). Relational databases link tables using foreign keys.

Basic SQL:

`SELECT * FROM students WHERE grade = 'A';` — retrieve records

`INSERT INTO students VALUES (1, 'Fatima', 'A');` — add a record

`UPDATE students SET grade = 'B' WHERE id = 1;` — modify a record

`DELETE FROM students WHERE id = 1;` — remove a record

Data validation: checks data is reasonable (range check, type check, presence check, length check). **Verification:** checks data was entered correctly (double entry, proofreading).

Key Points to Remember

1Integer, real, string, Boolean, date/time — key data types
2Record = full entry; field = one item; key field = unique ID
3SQL: SELECT, INSERT, UPDATE, DELETE
4Validation checks data is reasonable; verification checks it was entered correctly

Pakistan Example

NADRA — Pakistan's National Database and Data Management

NADRA (National Database and Registration Authority) manages 220+ million Pakistanis' records. Each citizen has a unique CNIC (key field). Fields include name, date of birth, address, and fingerprint data. NADRA uses relational databases to link CNIC to passport, driving licence, and tax records — real-world database design on a national scale.

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