Dalia-assignment-week3

Week3/assignment3/answers ex1.md

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+✅ 3.1 – Normalization Exercise
+Which columns violate 1NF?
+
+1NF requires:
+
+No repeating groups
+
+No multivalued attributes
+
+Atomic values
+
+Violations:
+
+food_code → contains multiple codes (e.g., C1, C2)
+
+food_description → contains multiple values (e.g., Curry, Cake)
+
+dinner_date → inconsistent date formats (not strictly 1NF violation, but bad practice)
+
+2. Extracted Entities
+
+Member
+
+Dinner
+
+Venue
+
+Food
+
+Member–Dinner (many-to-many)
+
+Dinner–Food (many-to-many)
+
+3. 3NF Tables
+Member
+
+member_id (PK)
+
+member_name
+
+member_address
+
+Venue
+
+venue_code (PK)
+
+venue_description
+
+Dinner
+
+dinner_id (PK)
+
+dinner_date
+
+venue_code (FK → Venue)
+
+Food
+
+food_code (PK)
+
+food_description
+
+MemberDinner
+
+member_id (FK)
+
+dinner_id (FK)
+PK: (member_id, dinner_id)
+
+DinnerFood
+
+dinner_id (FK)
+
+food_code (FK)
+PK: (dinner_id, food_code)

Week3/assignment3/exercise2/transaction.js

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+const mysql = require("mysql2/promise");
+
+async function main() {
+  const conn = await mysql.createConnection({
+    host: "localhost",
+    user: "root",
+    password: "",
+    database: "bankdb",
+  });
+
+  try {
+    await conn.beginTransaction();
+
+    // debit sender
+    await conn.execute(`
+      UPDATE account SET balance = balance - 1000 WHERE account_number = 101
+    `);
+
+    // credit receiver
+    await conn.execute(`
+      UPDATE account SET balance = balance + 1000 WHERE account_number = 102
+    `);
+
+    // log changes
+    await conn.execute(
+      `INSERT INTO account_changes (account_number, amount, remark)
+       VALUES (101, -1000, 'Money transferred to 102'),
+              (102, 1000, 'Money received from 101')`
+    );
+
+    await conn.commit();
+    console.log("Transaction completed.");
+  } catch (err) {
+    await conn.rollback();
+    console.error("Transaction rolled back:", err);
+  }
+
+  conn.end();
+}
+
+main();

Week3/assignment3/exercise2/transactions-create-tables.js

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+const mysql = require("mysql2/promise");
+
+async function main() {
+  const conn = await mysql.createConnection({
+    host: "localhost",
+    user: "root",
+    password: "",
+    database: "bankdb",
+  });
+
+  await conn.execute(`
+    CREATE TABLE IF NOT EXISTS account (
+      account_number INT PRIMARY KEY,
+      balance DECIMAL(10,2) NOT NULL
+    )
+  `);
+
+  await conn.execute(`
+    CREATE TABLE IF NOT EXISTS account_changes (
+      change_number INT AUTO_INCREMENT PRIMARY KEY,
+      account_number INT,
+      amount DECIMAL(10,2),
+      changed_date TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
+      remark VARCHAR(255),
+      FOREIGN KEY (account_number) REFERENCES account(account_number)
+    )
+  `);
+
+  console.log("Tables created.");
+  conn.end();
+}
+
+main();

Week3/assignment3/exercise2/transactions-insert-values.js

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+const mysql = require("mysql2/promise");
+
+async function main() {
+  const conn = await mysql.createConnection({
+    host: "localhost",
+    user: "root",
+    password: "",
+    database: "bankdb",
+  });
+
+  await conn.execute(
+    `INSERT INTO account (account_number, balance)
+     VALUES (101, 5000), (102, 2000)`
+  );
+
+  console.log("Sample data inserted.");
+  conn.end();
+}
+
+main();

Week3/assignment3/exercise4/.env.example

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+MONGO_URI="your mongodb connection string"
+DB_NAME="databaseWeek3"
+COLLECTION="bob_ross_episodes"

Week3/assignment3/exercise4/index.js

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+require("dotenv").config();
+const { MongoClient } = require("mongodb");
+const seedDatabase = require("./seedDatabase");
+
+const uri = process.env.MONGO_URI;
+const dbName = process.env.DB_NAME;
+const collectionName = process.env.COLLECTION;
+
+async function main() {
+  const client = new MongoClient(uri);
+  await client.connect();
+
+  const db = client.db(dbName);
+  const episodes = db.collection(collectionName);
+
+  await seedDatabase(db);
+
+  console.log("All episodes:");
+  console.log(await episodes.find().toArray());
+
+  // CREATE
+  await episodes.insertOne({ title: "New Painting", elements: ["tree", "lake"] });
+
+  // READ
+  const ep = await episodes.findOne({ title: "New Painting" });
+  console.log("Created:", ep);
+
+  // UPDATE
+  await episodes.updateOne(
+    { title: "New Painting" },
+    { $set: { elements: ["tree", "cloud"] } }
+  );
+
+  // DELETE
+  await episodes.deleteOne({ title: "New Painting" });
+
+  client.close();
+}
+
+main();

Week3/assignment3/exercise4/package.json

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+{
+  "dependencies": {
+    "dotenv": "^17.2.3",
+    "mongodb": "^6.21.0"
+  }
+}