Added solution

solution.sql

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+-- ============================================
+-- LAB | SQL Normalization, DDL & Aggregation
+-- Full Solution
+-- ============================================
+
+-- ============================================
+-- CLEANUP
+-- ============================================
+
+DROP TABLE IF EXISTS bookings;
+DROP TABLE IF EXISTS flights;
+DROP TABLE IF EXISTS aircrafts;
+DROP TABLE IF EXISTS customers;
+
+DROP TABLE IF EXISTS posts;
+DROP TABLE IF EXISTS authors;
+
+-- ============================================
+-- EXERCISE 1: BLOG DATABASE (3NF)
+-- ============================================
+
+CREATE TABLE authors (
+    author_id INT PRIMARY KEY GENERATED ALWAYS AS IDENTITY,
+    author_name VARCHAR(100) NOT NULL UNIQUE
+);
+
+CREATE TABLE posts (
+    post_id INT PRIMARY KEY GENERATED ALWAYS AS IDENTITY,
+    title VARCHAR(200) NOT NULL UNIQUE,
+    word_count INT NOT NULL CHECK (word_count >= 0),
+    views INT NOT NULL CHECK (views >= 0),
+    author_id INT NOT NULL,
+    CONSTRAINT fk_posts_author
+        FOREIGN KEY (author_id) REFERENCES authors(author_id)
+);
+
+-- ============================================
+-- SAMPLE DATA FOR BLOG DATABASE
+-- ============================================
+
+INSERT INTO authors (author_name) VALUES
+('Maria Charlotte'),
+('Juan Perez'),
+('Gemma Alcocer');
+
+INSERT INTO posts (title, word_count, views, author_id) VALUES
+('Best Paint Colors', 814, 14, 1),
+('Small Space Decorating Tips', 1146, 221, 2),
+('Hot Accessories', 986, 105, 1),
+('Mixing Textures', 765, 22, 1),
+('Kitchen Refresh', 1242, 307, 2),
+('Homemade Art Hacks', 1002, 193, 1),
+('Refinishing Wood Floors', 1571, 7542, 3);
+
+-- ============================================
+-- EXERCISE 2: AIRLINE DATABASE (3NF)
+-- ============================================
+
+CREATE TABLE customers (
+    id INT PRIMARY KEY GENERATED ALWAYS AS IDENTITY,
+    name VARCHAR(100) NOT NULL UNIQUE,
+    status VARCHAR(20) NOT NULL CHECK (status IN ('None', 'Silver', 'Gold')),
+    total_mileage INT NOT NULL CHECK (total_mileage >= 0)
+);
+
+CREATE TABLE aircrafts (
+    id INT PRIMARY KEY GENERATED ALWAYS AS IDENTITY,
+    name VARCHAR(100) NOT NULL UNIQUE,
+    total_seats INT NOT NULL CHECK (total_seats > 0)
+);
+
+CREATE TABLE flights (
+    flight_number VARCHAR(10) PRIMARY KEY,
+    aircraft_id INT NOT NULL,
+    mileage INT NOT NULL CHECK (mileage >= 0),
+    CONSTRAINT fk_flights_aircraft
+        FOREIGN KEY (aircraft_id) REFERENCES aircrafts(id)
+);
+
+CREATE TABLE bookings (
+    id INT PRIMARY KEY GENERATED ALWAYS AS IDENTITY,
+    customer_id INT NOT NULL,
+    flight_number VARCHAR(10) NOT NULL,
+    CONSTRAINT fk_bookings_customer
+        FOREIGN KEY (customer_id) REFERENCES customers(id),
+    CONSTRAINT fk_bookings_flight
+        FOREIGN KEY (flight_number) REFERENCES flights(flight_number),
+    CONSTRAINT uq_customer_flight UNIQUE (customer_id, flight_number)
+);
+
+-- ============================================
+-- SAMPLE DATA FOR AIRLINE DATABASE
+-- ============================================
+
+-- Aircrafts
+INSERT INTO aircrafts (name, total_seats) VALUES
+('Boeing 747', 400),
+('Airbus A330', 236),
+('Boeing 777', 264),
+('Boeing 747 (531 seats variant)', 531);
+
+-- Customers
+INSERT INTO customers (name, status, total_mileage) VALUES
+('Agustine Riviera', 'Silver', 115235),
+('Alaina Sepulvida', 'None', 6008),
+('Tom Jones', 'Gold', 205767),
+('Sam Rio', 'None', 2653),
+('Jessica James', 'Silver', 127656),
+('Ana Janco', 'Silver', 136773),
+('Jennifer Cortez', 'Gold', 300582),
+('Christian Janco', 'Silver', 14642);
+
+-- Flights
+INSERT INTO flights (flight_number, aircraft_id, mileage) VALUES
+('DL143', 1, 135),
+('DL122', 2, 4370),
+('DL53', 3, 2078),
+('DL222', 3, 1765),
+('DL37', 4, 531);
+
+-- Bookings
+INSERT INTO bookings (customer_id, flight_number) VALUES
+(1, 'DL143'),
+(1, 'DL122'),
+(2, 'DL122'),
+(3, 'DL122'),
+(3, 'DL53'),
+(4, 'DL143'),
+(3, 'DL222'),
+(5, 'DL143'),
+(6, 'DL222'),
+(7, 'DL222'),
+(5, 'DL122'),
+(4, 'DL37'),
+(8, 'DL222');
+
+-- ============================================
+-- EXTRA CHALLENGE: INDEXES
+-- ============================================
+
+CREATE INDEX idx_customers_status ON customers(status);
+CREATE INDEX idx_flights_aircraft_id ON flights(aircraft_id);
+CREATE INDEX idx_bookings_customer_id ON bookings(customer_id);
+CREATE INDEX idx_bookings_flight_number ON bookings(flight_number);
+
+-- ============================================
+-- EXERCISE 3: SQL QUERIES ON AIRLINE DATABASE
+-- ============================================
+
+-- 1. Total number of flights
+SELECT COUNT(DISTINCT flight_number) AS total_flights
+FROM flights;
+
+-- 2. Average flight distance
+SELECT AVG(mileage) AS avg_flight_distance
+FROM flights;
+
+-- 3. Average number of seats per aircraft
+SELECT AVG(total_seats) AS avg_seats_per_aircraft
+FROM aircrafts;
+
+-- 4. Average miles flown by customers, grouped by status
+SELECT status, AVG(total_mileage) AS avg_customer_mileage
+FROM customers
+GROUP BY status;
+
+-- 5. Max miles flown by customers, grouped by status
+SELECT status, MAX(total_mileage) AS max_customer_mileage
+FROM customers
+GROUP BY status;
+
+-- 6. Number of aircrafts with "Boeing" in their name
+SELECT COUNT(*) AS boeing_aircraft_count
+FROM aircrafts
+WHERE name LIKE '%Boeing%';
+
+-- 7. Flights with distance between 300 and 2000 miles
+SELECT *
+FROM flights
+WHERE mileage BETWEEN 300 AND 2000;
+
+-- 8. Average flight distance booked, grouped by customer status
+SELECT c.status, AVG(f.mileage) AS avg_booked_distance
+FROM bookings b
+JOIN customers c ON b.customer_id = c.id
+JOIN flights f ON b.flight_number = f.flight_number
+GROUP BY c.status;
+
+-- 9. Most booked aircraft among Gold status members
+SELECT a.name, COUNT(*) AS total_bookings
+FROM bookings b
+JOIN customers c ON b.customer_id = c.id
+JOIN flights f ON b.flight_number = f.flight_number
+JOIN aircrafts a ON f.aircraft_id = a.id
+WHERE c.status = 'Gold'
+GROUP BY a.name
+ORDER BY total_bookings DESC
+LIMIT 1;