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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+# This is an example .env file. We use .env files to store data that describes the environment the code needs to run on.
+# For this exercise we need a MONGODB_URL, so:
+# - make a copy of this file, call it `.env`
+# - look up how to connect to your database in atlas, there is a nice `connect` button that will help you out
+# - fill in the link to your new database. Make sure the database is `databaseWeek3`!
+
+MONGODB_URL=mongodb+srv://Dalia:Dal12345@sad@cluster0.aov8qkx.mongodb.net/?appName=Cluster0

Week3/assignment3/exercise4/index.js

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+require("dotenv").config();
+const { MongoClient, ServerApiVersion } = require("mongodb");
+const { seedDatabase } = require("./seedDatabase.js");
+
+async function createEpisodeExercise(client) {
+  // Add season 9 episode 13
+  const newEpisode = {
+    episode: "S09E13",
+    title: "MOUNTAIN HIDE-AWAY",
+    elements: [
+      "CIRRUS", "CLOUDS", "CONIFER", "DECIDIOUS", "GRASS",
+      "MOUNTAIN", "MOUNTAINS", "RIVER", "SNOWY_MOUNTAIN",
+      "TREE", "TREES"
+    ]
+  };
+  const result = await client
+    .db("databaseWeek3")
+    .collection("bob_ross_episodes")
+    .insertOne(newEpisode);
+
+  console.log(
+    `Created season 9 episode 13 and the document got the id ${result.insertedId}`
+  );
+}
+
+async function findEpisodesExercises(client) {
+  const collection = client.db("databaseWeek3").collection("bob_ross_episodes");
+
+  // Title of episode 2 in season 2
+  const ep2S2 = await collection.findOne({ episode: "S02E02" });
+  console.log(`The title of episode 2 in season 2 is ${ep2S2.title}`);
+
+  // Episode called BLACK RIVER
+  const blackRiver = await collection.findOne({ title: "BLACK RIVER" });
+  console.log(
+    `The season and episode number of the "BLACK RIVER" episode is ${blackRiver.episode}`
+  );
+
+  // All episodes where Bob Ross painted a CLIFF
+  const cliffEpisodes = await collection
+    .find({ elements: "CLIFF" })
+    .toArray();
+  console.log(
+    `The episodes that Bob Ross painted a CLIFF are ${cliffEpisodes
+      .map((e) => e.title)
+      .join(", ")}`
+  );
+
+  // All episodes where Bob Ross painted both a CLIFF and a LIGHTHOUSE
+  const cliffLighthouseEpisodes = await collection
+    .find({ elements: { $all: ["CLIFF", "LIGHTHOUSE"] } })
+    .toArray();
+  console.log(
+    `The episodes that Bob Ross painted a CLIFF and a LIGHTHOUSE are ${cliffLighthouseEpisodes
+      .map((e) => e.title)
+      .join(", ")}`
+  );
+}
+
+async function updateEpisodeExercises(client) {
+  const collection = client.db("databaseWeek3").collection("bob_ross_episodes");
+
+  // Correct the title of episode S30E13
+  const updateEpisode = await collection.updateOne(
+    { episode: "S30E13" },
+    { $set: { title: "BLUE RIDGE FALLS" } }
+  );
+  console.log(
+    `Ran a command to update episode 13 in season 30 and it updated ${updateEpisode.modifiedCount} episodes`
+  );
+
+  // Change all elements labeled BUSHES to BUSH
+  const updateBushes = await collection.updateMany(
+    { elements: "BUSHES" },
+    { $set: { "elements.$": "BUSH" } }
+  );
+  console.log(
+    `Ran a command to update all the BUSHES to BUSH and it updated ${updateBushes.modifiedCount} episodes`
+  );
+}
+
+async function deleteEpisodeExercise(client) {
+  const collection = client.db("databaseWeek3").collection("bob_ross_episodes");
+
+  // Delete episode S31E14
+  const deleteResult = await collection.deleteOne({ episode: "S31E14" });
+  console.log(
+    `Ran a command to delete episode and it deleted ${deleteResult.deletedCount} episodes`
+  );
+}
+
+async function main() {
+  if (!process.env.MONGODB_URL) {
+    throw Error(
+      "You did not set up the environment variables correctly. Please create a '.env' file."
+    );
+  }
+
+  const client = new MongoClient(process.env.MONGODB_URL, {
+  serverApi: ServerApiVersion.v1,
+});
+
+
+  try {
+    await client.connect();
+
+    // Seed the database
+    await seedDatabase(client);
+
+    // CREATE
+    await createEpisodeExercise(client);
+
+    // READ
+    await findEpisodesExercises(client);
+
+    // UPDATE
+    await updateEpisodeExercises(client);
+
+    // DELETE
+    await deleteEpisodeExercise(client);
+  } catch (err) {
+    console.error(err);
+  } finally {
+    await client.close();
+  }
+}
+
+main();
+
+
+/**
+ * In the end the console should read something like this: 
+
+Created season 9 episode 13 and the document got the id 625e9addd11e82a59aa9ff93
+The title of episode 2 in season 2 is WINTER SUN
+The season and episode number of the "BLACK RIVER" episode is S02E06
+The episodes that Bob Ross painted a CLIFF are NIGHT LIGHT, EVENING SEASCAPE, SURF'S UP, CLIFFSIDE, BY THE SEA, DEEP WILDERNESS HOME, CRIMSON TIDE, GRACEFUL WATERFALL
+The episodes that Bob Ross painted a CLIFF and a LIGHTHOUSE are NIGHT LIGHT
+Ran a command to update episode 13 in season 30 and it updated 1 episodes
+Ran a command to update all the BUSHES to BUSH and it updated 120 episodes
+Ran a command to delete episode and it deleted 1 episodes
+
+*/