Tugbanur- Database week4

Week3/assignment/exercise1.md

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+1.What columns violate 1NF?
+
+- food_code and food_description column. Because they both contain multiple values.
+
+  2.What entities do you recognize that could be extracted?
+
+- members, dinners, venues, food
+
+  3.Name all the tables and columns that would make a 3NF compliant solution.
+
+- Members => member_id, member_name, member_address
+- Dinners => dinner_id, dinner_date
+- Venues => venue_code, venue_description
+- Foods => food_code, food_description
+- Dinner_Venue => dinner_id, venue_code
+- Dinner_Food => dinner_id, food_code
+- Member_Dinner => member_id, dinner_id

Week3/assignment/exercise2/transaction.js

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+const mysql = require("mysql2/promise");
+
+async function transferAmount() {
+  const connection = await mysql.createConnection({
+    host: "localhost",
+    user: "hyfuser",
+    password: "hyfpassword",
+    database: "transaction_db",
+  });
+
+  try {
+    await connection.beginTransaction();
+
+    await connection.execute(`
+        UPDATE account
+        SET balance = balance -  1000
+        WHERE account_number = 101;
+        `);
+
+    await connection.execute(`
+            INSERT INTO account_changes (account_number, amount, remark)
+            VALUES (101, -1000, 'Transfer to account 102');
+          `);
+
+    await connection.execute(`
+        UPDATE account
+        SET balance = balance + 1000
+        WHERE account_number = 102;
+        `);
+
+    await connection.execute(`
+            INSERT INTO account_changes (account_number, amount, remark)
+            VALUES (102, 1000, 'Transfer from account 101');
+          `);
+
+    await connection.commit();
+    console.log("Transfer successful!");
+  } catch (error) {
+    await connection.rollback();
+    console.error("Transfer failed:", error.message);
+  } finally {
+    await connection.end();
+  }
+}
+
+transferAmount();

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

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+const mysql = require("mysql2/promise");
+
+async function createTables() {
+  const connection = await mysql.createConnection({
+    host: "localhost",
+    user: "hyfuser",
+    password: "hyfpassword",
+    database: "transaction_db",
+  });
+  await connection.execute(`
+CREATE TABLE IF NOT EXISTS account (
+account_number INT PRIMARY KEY,
+balance DECIMAL(15, 2) NOT NULL 
+);
+`);
+
+  await connection.execute(`
+CREATE TABLE IF NOT EXISTS account_changes (
+change_number INT AUTO_INCREMENT PRIMARY KEY,
+account_number INT,
+amount DECIMAL(15, 2),
+changed_date INTEGER,
+remark VARCHAR(255),
+FOREIGN KEY (account_number) REFERENCES account(account_number)
+);
+`);
+
+  await connection.end();
+}
+
+createTables().catch(console.error);

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

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+const mysql = require("mysql2/promise");
+
+async function insertTables() {
+  const connection = await mysql.createConnection({
+    host: "localhost",
+    user: "hyfuser",
+    password: "hyfpassword",
+    database: "transaction_db",
+  });
+  await connection.execute(`
+    INSERT INTO account (account_number, balance) VALUES
+    (101, 5000.00),
+    (102, 3000.00);
+     `);
+  await connection.end();
+}
+
+insertTables().catch(console.error);

Week3/assignment/exercise3.js

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+function getPopulation(Country, name, code, cb) {
+  // assuming that connection to the database is established and stored as conn
+  const query = `SELECT Population FROM ?? WHERE Name = ? and code = ?`;
+  const values = [Country, name, code];
+
+  conn.query(query, values, (err, result) => {
+    if (err) return cb(err);
+    if (result.length === 0) return cb(new Error("Not found"));
+    cb(null, result[0].Population);
+  });
+}

Week3/assignment/exercise4/bobRossEpisode.js

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+import mongoose from "mongoose";
+const { Schema } = mongoose;
+
+const episodeSchema = new Schema({
+  _id: {
+    type: Schema.Types.ObjectId,
+    default: () => new mongoose.Types.ObjectId(),
+  },
+  title: String,
+  season: Number,
+  episode: Number,
+  elements: [String],
+});
+
+const BobRossEpisode = mongoose.model("BobRossEpisode", episodeSchema);
+export default BobRossEpisode;

Week3/assignment/exercise4/index.js

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+import mongoose from "mongoose";
+import dotenv from "dotenv";
+import BobRossEpisode from "./bobRossEpisode.js";
+
+dotenv.config();
+
+mongoose
+  .connect(process.env.MONGODB_URI, {
+    useNewUrlParser: true,
+    useUnifiedTopology: true,
+  })
+  .then(() => console.log("Connected to MongoDB"))
+  .catch((err) => console.error("Could not connect to MongoDB", err));
+
+async function addEpisode(data) {
+  const episode = new BobRossEpisode(data);
+  await episode.save();
+  console.log("Episode added:", episode);
+}
+
+addEpisode({
+  title: "Mountain Retreat",
+  season: 3,
+  episode: 5,
+  elements: ["mountain", "trees", "clouds"],
+});
+
+async function findAllEpisodes() {
+  const episodes = await BobRossEpisode.find();
+  console.log("All episodes:", episodes);
+}
+
+findAllEpisodes();
+
+async function updateEpisode(id, data) {
+  const episode = await BobRossEpisode.findByIdAndUpdate(id, data, {
+    new: true,
+    runValidators: true,
+  });
+  if (episode) {
+    console.log("Updated episode:", episode);
+  } else {
+    console.log("Updated episode:", episode);
+  }
+}
+updateEpisode("61426985e216000000477259");
+
+async function deleteEpisode(id) {
+  const episode = await BobRossEpisode.findByIdAndDelete(id);
+  if (episode) {
+    console.log("Episode deleted");
+  } else {
+    console.log("Episode not found");
+  }
+}
+
+deleteEpisode("61426985e216000000477259");