SQL LAB

Exercise1.sql

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+-- STEP1
+-- Raw table has redundancy: author name repeated across multiple posts
+-- Normalization to 3NF requires separating authors from posts
+
+-- 1NF: each cell has one value, each row is unique ✓
+-- 2NF: add surrogate keys to eliminate partial dependencies
+-- 3NF: separate author data into its own table (author info depends on author, not on post)
+--
+
+--Step2
+--Write the DDL 
+CREATE TABLE authors (
+    id      INT PRIMARY KEY AUTO_INCREMENT,
+    name    VARCHAR(255) NOT NULL);
+
+CREATE TABLE posts (
+    id          INT PRIMARY KEY AUTO_INCREMENT,
+    author_id   INT NOT NULL,
+    title       VARCHAR(255) NOT NULL,
+    word_count  INT,
+    views       INT,
+    FOREIGN KEY (author_id) REFERENCES authors(id));    
+
+
+
+--Step3
+
+INSERT INTO authors (name) VALUES
+('Mario Wu'),
+('Jospe Perez'),
+('Emma Houng');
+
+INSERT INTO posts (author_id, title, word_count, views) VALUES
+(1, 'Best Paint Colors',           814,  14),
+(2, 'Small Space Decorating Tips', 1146, 221),
+(1, 'Hot Accessories',             986,  105),
+(1, 'Mixing Textures',             765,  22),
+(2, 'Kitchen Refresh',             1242, 307),
+(1, 'Homemade Art Hacks',          1002, 193),
+(3, 'Refinishing Wood Floors',     1571, 7542);

Exercise2.sql

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+STEP1/2
+
+-- Raw table has three independent entities mixed together:
+--   - Customer (name, status, total_mileage) → depends only on customer
+--   - Aircraft (name, total_seats) → depends only on aircraft
+--   - Flight (flight_number, mileage, aircraft) → depends only on flight
+--   - Booking → junction between customer and flight
+--
+
+-- STEP3 
+
+-- Aircrafts table
+
+CREATE TABLE aircrafts (
+    id          INT PRIMARY KEY AUTO_INCREMENT,
+    name        VARCHAR(100) NOT NULL,
+    total_seats INT NOT NULL);
+
+-- Customers table
+
+CREATE TABLE customers (
+    id              INT PRIMARY KEY AUTO_INCREMENT,
+    name            VARCHAR(255) NOT NULL,
+    status          VARCHAR(50),
+    total_mileage   INT);
+
+-- Flights table (references aircraft)
+
+CREATE TABLE flights (
+    flight_number   VARCHAR(10) PRIMARY KEY,
+    aircraft_id     INT NOT NULL,
+    mileage         INT NOT NULL,
+    FOREIGN KEY (aircraft_id) REFERENCES aircrafts(id));
+
+-- Bookings table (junction: customer ↔ flight)
+
+CREATE TABLE bookings (
+    id              INT PRIMARY KEY AUTO_INCREMENT,
+    customer_id     INT NOT NULL,
+    flight_number   VARCHAR(10) NOT NULL,
+    FOREIGN KEY (customer_id) REFERENCES customers(id),
+    FOREIGN KEY (flight_number) REFERENCES flights(flight_number));
+
+-- STEP4
+
+INSERT INTO aircrafts (name, total_seats) VALUES
+('Boeing 747',  120),
+('Airbus A330', 216),
+('Boeing 777',  344);
+
+INSERT INTO customers (name, status, total_mileage) VALUES
+('Agustine Riviera', 'Silver', 1788235),
+('Alaina Sepulvida', NULL,     62028),
+('Tom Jones',        'Gold',   1345767),
+('Sam Rio',          NULL,     269653),
+('Jessica James',    'Silver', 1278676),
+('Ana Janco',        'Silver', 13233273),
+('Jennifer Cortez',  'Gold',   3220582),
+('Christian Janco',  'Silver', 1466742);
+
+INSERT INTO flights (flight_number, aircraft_id, mileage) VALUES
+('DL143', 1, 1323),
+('DL122', 2, 3479),
+('DL53',  3, 2988),
+('DL222', 3, 10065),
+('DL37',  1, 539);
+
+INSERT INTO bookings (customer_id, flight_number) VALUES
+(1, 'DL143'),
+(1, 'DL121'),
+(2, 'DL122'),
+(3, 'DL123'),
+(3, 'DL53'),
+(3, 'DL242'),
+(4, 'DL143'),
+(4, 'DL37'),
+(5, 'DL143'),
+(5, 'DL142'),
+(6, 'DL222'),
+(7, 'DL222'),
+(8, 'DL262');

Exercise3.sql

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+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_mileage
+FROM customers
+GROUP BY status;
+
+-- 5. Max miles flown by customers, grouped by status
+SELECT status, MAX(total_mileage) AS max_mileage
+FROM customers
+GROUP BY status;
+
+-- 6. Number of aircrafts with "Boeing" in their name
+SELECT COUNT(*) AS boeing_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;