Igor w2 databases

Week1/databases/connectDatabases.js

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+import pkg from "pg";
+const { Client } = pkg;
+
+export async function connectDB(database = "world") {
+  const client = new Client({
+    user: "hyfuser",
+    host: "localhost",
+    database: database,
+    password: "hyfpassword",
+    port: 5432,
+  });
+
+  try {
+    await client.connect();
+    console.log(`Connected to database: ${client.database}`);
+    return client;
+  } catch (error) {
+    console.error("Connection error:", error);
+    throw error;
+  }
+}

Week1/databases/exercise2_world.js

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+import { connectDB } from "./connectDatabase.js";
+
+async function runQueries() {
+  const client = await connectDB("world");
+
+  try {
+    const q1 = await client.query(
+      `SELECT name FROM country WHERE population > 8000000;`
+    );
+    console.log("1. Countries > 8M:", q1.rows);
+
+    const q2 = await client.query(
+      `SELECT name FROM country WHERE name ILIKE '%land%';`
+    );
+    console.log("2. Countries with 'land':", q2.rows);
+
+    const q3 = await client.query(
+      `SELECT name FROM city WHERE population BETWEEN 500000 AND 1000000;`
+    );
+    console.log("3. Cities 500k–1M:", q3.rows);
+
+    const q4 = await client.query(
+      `SELECT name FROM country WHERE continent = 'Europe';`
+    );
+    console.log("4. European countries:", q4.rows);
+
+    const q5 = await client.query(
+      `SELECT name FROM country ORDER BY surfacearea DESC;`
+    );
+    console.log("5. Countries by surface area DESC:", q5.rows);
+
+    const q6 = await client.query(
+      `SELECT name FROM city WHERE countrycode = 'NLD';`
+    );
+    console.log("6. Cities in Netherlands:", q6.rows);
+
+    const q7 = await client.query(
+      `SELECT population FROM city WHERE name = 'Rotterdam';`
+    );
+    console.log("7. Population of Rotterdam:", q7.rows);
+
+    const q8 = await client.query(`
+      SELECT name FROM country ORDER BY surfacearea DESC LIMIT 10;
+    `);
+    console.log("8. Top 10 countries by surface area:", q8.rows);
+
+    const q9 = await client.query(`
+      SELECT name FROM city ORDER BY population DESC LIMIT 10;
+    `);
+    console.log("9. Top 10 most populated cities:", q9.rows);
+
+    const q10 = await client.query(
+      `SELECT SUM(population) AS world_population FROM country;`
+    );
+    console.log("10. World population:", q10.rows[0].world_population);
+  } catch (err) {
+    console.error("Query error:", err);
+  } finally {
+    await client.end();
+    console.log("Connection closed.");
+  }
+}
+
+runQueries();

Week1/databases/setupMeetup.js

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+import pkg from "pg";
+const { Client } = pkg;
+
+const defaultClient = new Client({
+  user: "hyfuser",
+  host: "localhost",
+  database: "postgres",
+  password: "hyfpassword",
+  port: 5432,
+});
+
+async function setupDatabase() {
+  let client;
+  try {
+    await defaultClient.connect();
+
+    await defaultClient.query(`DROP DATABASE IF EXISTS meetup;`);
+    await defaultClient.query(`CREATE DATABASE meetup;`);
+    console.log('Database "meetup" created.');
+
+    await defaultClient.end();
+
+    client = new Client({
+      user: "hyfuser",
+      host: "localhost",
+      database: "meetup",
+      password: "hyfpassword",
+      port: 5432,
+    });
+    await client.connect();
+
+    await client.query(`
+      CREATE TABLE Invitee (
+        invitee_no INTEGER GENERATED BY DEFAULT AS IDENTITY PRIMARY KEY,
+        invitee_name VARCHAR(100),
+        invited_by VARCHAR(100)
+      );
+    `);
+
+    await client.query(`
+      CREATE TABLE Room (
+        room_no INT PRIMARY KEY,
+        room_name VARCHAR(64),
+        floor_number SMALLINT
+      );
+    `);
+
+    await client.query(`
+      CREATE TABLE Meeting (
+        meeting_no INTEGER GENERATED BY DEFAULT AS IDENTITY PRIMARY KEY,
+        meeting_title VARCHAR(64),
+        starting_time TIMESTAMP,
+        ending_time TIMESTAMP,
+        room_no INT REFERENCES Room(room_no)
+      );
+    `);
+
+    console.log("Tables created.");
+
+    await client.query(`
+  INSERT INTO Invitee (invitee_name, invited_by) VALUES
+    ('Alice Johnson', 'Bob Smith'),
+    ('Bob Smith', 'Carol White'),
+    ('Carol White', 'David Lee'),
+    ('David Lee', 'Alice Johnson'),
+    ('Eve Brown', 'Bob Smith');
+`);
+
+    await client.query(`
+      INSERT INTO Room (room_name, floor_number) VALUES
+  ('Blue Room', 1),
+  ('Green Room', 1),
+  ('Yellow Room', 2),
+  ('Red Room', 2),
+  ('Conference Hall', 3);
+    `);
+
+    await client.query(`
+  INSERT INTO Meeting (meeting_title, starting_time, ending_time, room_no) VALUES
+  ('Project Kickoff', '2025-09-01 09:00:00', '2025-09-01 10:00:00', 1),
+  ('Design Review', '2025-09-02 11:00:00', '2025-09-02 12:30:00', 2),
+  ('Team Standup', '2025-09-03 09:30:00', '2025-09-03 10:00:00', 3),
+  ('Client Presentation', '2025-09-04 14:00:00', '2025-09-04 15:30:00', 4),
+  ('Retrospective', '2025-09-05 16:00:00', '2025-09-05 17:00:00', 5);
+`);
+
+    console.log("Sample data inserted.");
+  } catch (err) {
+    console.error("Error:", err);
+  } finally {
+    if (client) await client.end().catch(() => {});
+    await defaultClient.end().catch(() => {});
+    console.log("Setup complete (connections closed).");
+  }
+}
+
+setupDatabase();

Week1/recipes.sql

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+CREATE TABLE recipes (
+    recipe_id INT PRIMARY KEY AUTO_INCREMENT,
+    name VARCHAR(255) NOT NULL
+);
+
+CREATE TABLE categories (
+    category_id INT PRIMARY KEY AUTO_INCREMENT,
+    name VARCHAR(100) NOT NULL UNIQUE
+);
+
+CREATE TABLE ingredients (
+    ingredient_id INT PRIMARY KEY AUTO_INCREMENT,
+    name VARCHAR(100) NOT NULL UNIQUE
+);
+
+CREATE TABLE steps (
+    step_id INT PRIMARY KEY AUTO_INCREMENT,
+    description TEXT NOT NULL
+);
+
+CREATE TABLE recipe_category (
+    recipe_id INT,
+    category_id INT,
+    PRIMARY KEY (recipe_id, category_id),
+    FOREIGN KEY (recipe_id) REFERENCES recipes(recipe_id) ON DELETE CASCADE,
+    FOREIGN KEY (category_id) REFERENCES categories(category_id) ON DELETE CASCADE
+);
+
+CREATE TABLE recipe_ingredient (
+    recipe_id INT,
+    ingredient_id INT,
+    quantity VARCHAR(50),
+    PRIMARY KEY (recipe_id, ingredient_id),
+    FOREIGN KEY (recipe_id) REFERENCES recipes(recipe_id) ON DELETE CASCADE,
+    FOREIGN KEY (ingredient_id) REFERENCES ingredients(ingredient_id) ON DELETE CASCADE
+);
+
+CREATE TABLE recipe_step (
+    recipe_id INT,
+    step_id INT,
+    step_order INT NOT NULL,
+    PRIMARY KEY (recipe_id, step_id),
+    FOREIGN KEY (recipe_id) REFERENCES recipes(recipe_id) ON DELETE CASCADE,
+    FOREIGN KEY (step_id) REFERENCES steps(step_id) ON DELETE CASCADE
+);

Week2/databases/connectDatabase.js

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+import pkg from 'pg';
+const { Client } = pkg;
+
+
+export async function connectDB(database = 'postgres') {
+  const client = new Client({
+    user: 'hyfuser',
+    host: 'localhost',
+    database,
+    password: 'hyfpassword',
+    port: 5432,
+  });
+
+  try {
+    await client.connect();
+    console.log(`Connected to database: ${database}`);
+    return client;
+  } catch (error) {
+    console.error('Connection error:', error);
+    throw error;
+  }
+}

Week2/databases/exercise 1 Keys.js

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+import pkg from "pg";
+const { Client } = pkg;
+
+const client = new Client({
+  user: "postgres",
+  host: "localhost",
+  database: "hyf_db",
+  password: "your_password",
+  port: 5432,
+});
+
+async function main() {
+  try {
+    await client.connect();
+    console.log("Connected to the database");
+
+    await client.query(`
+      DO $$ 
+      BEGIN 
+        IF NOT EXISTS (SELECT 1 FROM pg_type WHERE typname = 'gender_type') THEN
+          CREATE TYPE gender_type AS ENUM ('Male', 'Female', 'Other');
+        END IF;
+      END $$;
+    `);
+
+    await client.query(`
+      CREATE TABLE IF NOT EXISTS authors (
+        author_id SERIAL PRIMARY KEY,
+        author_name VARCHAR(100) NOT NULL,
+        university VARCHAR(100),
+        date_of_birth DATE,
+        h_index INT,
+        gender gender_type,
+        mentor INT,
+        CONSTRAINT fk_mentor FOREIGN KEY (mentor) REFERENCES authors(author_id) ON DELETE SET NULL
+      );
+    `);
+
+    console.log(
+      "Authors table created with self-referencing mentor key and gender ENUM"
+    );
+  } catch (error) {
+    console.error("Error occurred:", error.message);
+  } finally {
+    await client.end();
+    console.log("Database connection closed");
+  }
+}
+
+main().catch((error) => {
+  console.error("Main function error:", error.message);
+});

Week2/databases/exercise 2 Relationships.js

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+import pkg from "pg";
+const { Client } = pkg;
+
+const client = new Client({
+  user: "postgres",
+  host: "localhost",
+  database: "hyf_db",
+  password: "your_password",
+  port: 5432,
+});
+
+async function main() {
+  try {
+    await client.connect();
+    console.log("Connected to the database");
+
+    await client.query(`
+      CREATE TABLE IF NOT EXISTS research_papers (
+        paper_id SERIAL PRIMARY KEY,
+        paper_title VARCHAR(255) NOT NULL,
+        conference VARCHAR(100),
+        publish_date DATE
+      );
+    `);
+
+    await client.query(`
+      CREATE TABLE IF NOT EXISTS author_papers (
+        author_id INT REFERENCES authors(author_id),
+        paper_id INT REFERENCES research_papers(paper_id),
+        PRIMARY KEY (author_id, paper_id)
+      );
+    `);
+
+    console.log("Research papers and author_papers tables created");
+
+    await client.query(`
+      INSERT INTO authors (author_name, university, date_of_birth, h_index, gender)
+      VALUES
+        ('Alice Smith', 'MIT', '1980-05-10', 42, 'Female'),
+        ('Bob Johnson', 'Stanford', '1975-09-20', 55, 'Male'),
+        ('Carol Lee', 'Harvard', '1985-01-15', 38, 'Female')
+      ON CONFLICT DO NOTHING;
+    `);
+
+    await client.query(`
+      INSERT INTO research_papers (paper_title, conference, publish_date)
+      VALUES
+        ('AI in Healthcare', 'NeurIPS', '2020-12-01'),
+        ('Quantum Computing Advances', 'QCon', '2021-06-15'),
+        ('Deep Learning Optimization', 'ICML', '2019-07-07')
+      ON CONFLICT DO NOTHING;
+    `);
+
+    await client.query(`
+      INSERT INTO author_papers (author_id, paper_id)
+      VALUES (1,1), (2,1), (1,2), (3,3)
+      ON CONFLICT DO NOTHING;
+    `);
+
+    console.log("Sample authors and papers inserted");
+  } catch (error) {
+    console.error("An error occurred:", error);
+    throw error; // Re-throw to allow caller to handle if needed
+  } finally {
+    await client.end();
+    console.log("Database connection closed");
+  }
+}
+
+main().catch((error) => {
+  console.error("Failed to execute main function:", error);
+  process.exit(1); // Exit with error code
+});