diff --git a/Week3/assignment/exercise1-normalization.md b/Week3/assignment/exercise1-normalization.md
new file mode 100644
index 000000000..99d31d1c2
--- /dev/null
+++ b/Week3/assignment/exercise1-normalization.md
@@ -0,0 +1,136 @@
+# Exercise 3.1 - SQL Normalization
+
+Original table:
+
+member_id | member_name | member_address | dinner_id | dinner_date | venue_code | venue_description | food_code  | food_description
+--------- | ----------- | -------------- | --------- | ----------- | ---------- | ----------------- | ---------- | ----------------
+...       | ...         | ...            | ...       | ...         | ...        | ...               | C1, C2     | Curry, Cake
+...       | ...         | ...            | ...       | ...         | ...        | ...               | P1, T1, M1 | Pie, Tea, Mousse
+etc.
+
+---
+
+## 1. Which columns violate 1NF?
+
+1NF (First Normal Form) requires:
+
+- Each field contains **atomic** (indivisible) values.
+- No repeating groups or lists in a single column.
+- All values in a column are of the same type.
+
+In this table, 1NF is violated by:
+
+- **food_code** - contains multiple values separated by commas, e.g. `C1, C2`, `P1, T1, M1`.
+- **food_description** - also contains multiple values separated by commas, e.g. `Curry, Cake`, `Pie, Tea, Mousse`.
+
+Additionally, **dinner_date** is stored in multiple different formats (`2020-03-15`, `20-03-2020`, `Mar 25 '20`), which is bad practice, but they are still single scalar values. The main 1NF violation is the multi-valued food columns.
+
+---
+
+## 2. Which entities can be extracted?
+
+From the table we can identify the following entities:
+
+1. **Member**
+    - member_id
+    - member_name
+    - member_address
+
+2. **Dinner (Event)**
+    - dinner_id
+    - dinner_date
+    - venue_code (the place where the dinner is held)
+
+3. **Venue**
+    - venue_code
+    - venue_description
+
+4. **Food**
+    - food_code
+    - food_description
+
+5. **MemberDinner / Attendance**
+    - which member attended which dinner  
+      (many-to-many relationship between Member and Dinner)
+
+6. **DinnerFood / Menu**
+    - which food items were served at a given dinner  
+      (many-to-many relationship between Dinner and Food)
+
+---
+
+## 3. Tables and columns for a 3NF-compliant solution
+
+Below is a 3NF schema.
+
+### 1. Table `members`
+
+- **member_id** (PK)
+- member_name
+- member_address
+
+Functional dependency:  
+`member_id → member_name, member_address`  
+No transitive dependencies.
+
+---
+
+### 2. Table `venues`
+
+- **venue_code** (PK)
+- venue_description
+
+Functional dependency:  
+`venue_code → venue_description`
+
+---
+
+### 3. Table `dinners`
+
+- **dinner_id** (PK)
+- dinner_date (DATE type)
+- venue_code (FK → venues.venue_code)
+
+Functional dependency:  
+`dinner_id → dinner_date, venue_code`
+
+---
+
+### 4. Table `foods`
+
+- **food_code** (PK)
+- food_description
+
+Functional dependency:  
+`food_code → food_description`
+
+---
+
+### 5. Table `member_dinners` (attendance)
+
+- **member_id** (FK → members.member_id)
+- **dinner_id** (FK → dinners.dinner_id)
+- (PK is the combination (member_id, dinner_id))
+
+This table represents which member attended which dinner (many-to-many).
+
+---
+
+### 6. Table `dinner_foods` (menu per dinner)
+
+- **dinner_id** (FK → dinners.dinner_id)
+- **food_code** (FK → foods.food_code)
+- (PK is the combination (dinner_id, food_code))
+
+This table replaces the multi-valued fields `food_code` and `food_description` by storing one row per dinner–food combination.
+
+---
+
+## Final 3NF schema
+
+- `members(member_id PK, member_name, member_address)`
+- `venues(venue_code PK, venue_description)`
+- `dinners(dinner_id PK, dinner_date, venue_code FK)`
+- `foods(food_code PK, food_description)`
+- `member_dinners(member_id FK, dinner_id FK, PK(member_id, dinner_id))`
+- `dinner_foods(dinner_id FK, food_code FK, PK(dinner_id, food_code))`
\ No newline at end of file
diff --git a/Week3/assignment/index.js b/Week3/assignment/index.js
new file mode 100644
index 000000000..61874975d
--- /dev/null
+++ b/Week3/assignment/index.js
@@ -0,0 +1,71 @@
+require("dotenv").config()
+const { MongoClient, ObjectId } = require("mongodb")
+
+const uri = process.env.MONGODB_URI
+
+if (!uri) {
+    throw new Error("Please set MONGODB_URI in your .env file")
+}
+
+async function main() {
+    const client = new MongoClient(uri)
+
+    try {
+        await client.connect()
+        console.log("Connected to MongoDB Atlas")
+
+        const db = client.db("databaseWeek3")
+        const episodes = db.collection("bob_ross_episodes")
+
+        const newEpisode = {
+            title: "My Custom Joy of Painting Episode",
+            season: 100,
+            episode: 1,
+            elements: ["happy little trees", "mountain", "lake"],
+            aired_on: new Date("2025-01-01"),
+        }
+
+        const insertResult = await episodes.insertOne(newEpisode)
+        console.log("Inserted new episode with _id:", insertResult.insertedId)
+
+
+        const insertedId = insertResult.insertedId
+        const foundById = await episodes.findOne({ _id: insertedId })
+
+        const cursor = episodes.find({ elements: "happy little trees" })
+        const episodesWithTrees = await cursor.toArray()
+
+        console.log(
+            `Episodes with "happy little trees": ${episodesWithTrees.length}`
+        )
+
+        const updateResult = await episodes.updateOne(
+            { _id: insertedId },
+            {
+                $set: {
+                    title: "Updated Custom Joy of Painting Episode",
+                    updated_at: new Date(),
+                },
+            }
+        )
+
+        console.log(
+            `Updated episodes: matched ${updateResult.matchedCount}, modified ${updateResult.modifiedCount}`
+        )
+
+        const updatedDoc = await episodes.findOne({ _id: insertedId })
+
+        const deleteResult = await episodes.deleteOne({ _id: insertedId })
+        console.log(`Deleted documents: ${deleteResult.deletedCount}`)
+    } catch (err) {
+        console.error("MongoDB error:", err)
+    } finally {
+        await client.close()
+        console.log("Connection to MongoDB closed")
+    }
+}
+
+main().catch((err) => {
+    console.error(err)
+    process.exit(1)
+})
\ No newline at end of file
diff --git a/Week3/assignment/package-lock.json b/Week3/assignment/package-lock.json
new file mode 100644
index 000000000..f71cceef5
--- /dev/null
+++ b/Week3/assignment/package-lock.json
@@ -0,0 +1,308 @@
+{
+  "name": "assignment",
+  "version": "1.0.0",
+  "lockfileVersion": 3,
+  "requires": true,
+  "packages": {
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+      "version": "1.0.0",
+      "license": "ISC",
+      "dependencies": {
+        "dotenv": "^17.2.3",
+        "mongodb": "^6.21.0",
+        "mysql2": "^3.15.3"
+      }
+    },
+    "node_modules/@mongodb-js/saslprep": {
+      "version": "1.3.2",
+      "resolved": "https://registry.npmjs.org/@mongodb-js/saslprep/-/saslprep-1.3.2.tgz",
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+      "dependencies": {
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+      }
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+      "version": "7.0.3",
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+      "license": "MIT"
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+      "license": "MIT",
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+      "license": "MIT",
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+      "license": "Apache-2.0",
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+      "license": "BSD-2-Clause",
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+      "license": "MIT",
+      "dependencies": {
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+      }
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+      "license": "MIT",
+      "dependencies": {
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+      },
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+      },
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+      "license": "MIT"
+    },
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+          "optional": true
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+        },
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+        },
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+        }
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+    },
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+      "dependencies": {
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+      },
+      "engines": {
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+    },
+    "node_modules/webidl-conversions": {
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+    }
+  }
+}
diff --git a/Week3/assignment/package.json b/Week3/assignment/package.json
new file mode 100644
index 000000000..c7166dcc3
--- /dev/null
+++ b/Week3/assignment/package.json
@@ -0,0 +1,17 @@
+{
+  "name": "assignment",
+  "version": "1.0.0",
+  "main": "index.js",
+  "scripts": {
+    "test": "echo \"Error: no test specified\" && exit 1"
+  },
+  "keywords": [],
+  "author": "",
+  "license": "ISC",
+  "description": "",
+  "dependencies": {
+    "dotenv": "^17.2.3",
+    "mongodb": "^6.21.0",
+    "mysql2": "^3.15.3"
+  }
+}
diff --git a/Week3/assignment/sql-injection.md b/Week3/assignment/sql-injection.md
new file mode 100644
index 000000000..5d5f71d87
--- /dev/null
+++ b/Week3/assignment/sql-injection.md
@@ -0,0 +1,16 @@
+# Exercise 3.3 — SQL Injection
+
+Original function:
+
+```js
+function getPopulation(Country, name, code, cb) {
+  // assuming that connection to the database is established and stored as conn
+  conn.query(
+    `SELECT Population FROM ${Country} WHERE Name = '${name}' and code = '${code}'`,
+    function (err, result) {
+      if (err) cb(err);
+      if (result.length == 0) cb(new Error("Not found"));
+      cb(null, result[0].name);
+    }
+  );
+}
\ No newline at end of file
diff --git a/Week3/assignment/transaction.js b/Week3/assignment/transaction.js
new file mode 100644
index 000000000..ca9c5a5a9
--- /dev/null
+++ b/Week3/assignment/transaction.js
@@ -0,0 +1,81 @@
+const mysql = require("mysql2/promise")
+
+async function main() {
+    const connection = await mysql.createConnection({
+        host: "localhost",
+        user: "root",
+        password: "1234",
+        database: "dbweek3",
+    })
+
+    const FROM_ACCOUNT = 101
+    const TO_ACCOUNT = 102
+    const AMOUNT = 1000.0
+
+    try {
+        await connection.beginTransaction()
+
+        const [rowsFrom] = await connection.execute(
+            "SELECT balance FROM account WHERE account_number = ? FOR UPDATE",
+            [FROM_ACCOUNT]
+        )
+        const [rowsTo] = await connection.execute(
+            "SELECT balance FROM account WHERE account_number = ? FOR UPDATE",
+            [TO_ACCOUNT]
+        )
+
+        if (rowsFrom.length === 0 || rowsTo.length === 0) {
+            throw new Error("One of the accounts does not exist.")
+        }
+
+        const fromBalance = parseFloat(rowsFrom[0].balance)
+
+        if (fromBalance < AMOUNT) {
+            throw new Error("Insufficient funds on source account.")
+        }
+
+        await connection.execute(
+            "UPDATE account SET balance = balance - ? WHERE account_number = ?",
+            [AMOUNT, FROM_ACCOUNT]
+        )
+
+        await connection.execute(
+            "UPDATE account SET balance = balance + ? WHERE account_number = ?",
+            [AMOUNT, TO_ACCOUNT]
+        )
+
+        await connection.execute(
+            `
+                INSERT INTO account_changes (account_number, amount, remark)
+                VALUES (?, ?, ?), (?, ?, ?)
+            `,
+            [
+                FROM_ACCOUNT,
+                -AMOUNT,
+                `Transfer to account ${TO_ACCOUNT}`,
+                TO_ACCOUNT,
+                AMOUNT,
+                `Transfer from account ${FROM_ACCOUNT}`,
+            ]
+        )
+
+        await connection.commit()
+        console.log(
+            `Transferred ${AMOUNT} from ${FROM_ACCOUNT} to ${TO_ACCOUNT} successfully.`
+        )
+    } catch (err) {
+        console.error("Error during transaction, rolling back:", err.message)
+        try {
+            await connection.rollback()
+        } catch (rollbackErr) {
+            console.error("Error during rollback:", rollbackErr.message)
+        }
+    } finally {
+        await connection.end()
+    }
+}
+
+main().catch((err) => {
+    console.error(err)
+    process.exit(1)
+})
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diff --git a/Week3/assignment/transactions-create-tables.js b/Week3/assignment/transactions-create-tables.js
new file mode 100644
index 000000000..1c712ba83
--- /dev/null
+++ b/Week3/assignment/transactions-create-tables.js
@@ -0,0 +1,47 @@
+
+const mysql = require("mysql2/promise")
+
+async function main() {
+    const connection = await mysql.createConnection({
+        host: "localhost",
+        user: "root",
+        password: "1234",
+        database: "dbweek3",
+    })
+
+    try {
+        await connection.execute("SET FOREIGN_KEY_CHECKS = 0")
+        await connection.execute("DROP TABLE IF EXISTS account_changes")
+        await connection.execute("DROP TABLE IF EXISTS account")
+        await connection.execute("SET FOREIGN_KEY_CHECKS = 1")
+
+        await connection.execute(`
+            CREATE TABLE account (
+                account_number INT PRIMARY KEY,
+                balance DECIMAL(10, 2) NOT NULL DEFAULT 0
+            )
+    `)
+
+        await connection.execute(`
+            CREATE TABLE account_changes (
+                change_number INT AUTO_INCREMENT PRIMARY KEY,
+                account_number INT NOT NULL,
+                amount DECIMAL(10, 2) NOT NULL,
+                changed_date DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
+                remark VARCHAR(255),
+                FOREIGN KEY (account_number) REFERENCES account(account_number)
+            )
+    `)
+
+        console.log("Tables 'account' and 'account_changes' created successfully.")
+    } catch (err) {
+        console.error("Error creating tables:", err)
+    } finally {
+        await connection.end()
+    }
+}
+
+main().catch((err) => {
+    console.error(err)
+    process.exit(1)
+})
\ No newline at end of file
diff --git a/Week3/assignment/transactions-insert-values.js b/Week3/assignment/transactions-insert-values.js
new file mode 100644
index 000000000..fc93c4692
--- /dev/null
+++ b/Week3/assignment/transactions-insert-values.js
@@ -0,0 +1,46 @@
+const mysql = require("mysql2/promise")
+
+async function main() {
+    const connection = await mysql.createConnection({
+        host: "localhost",
+        user: "root",
+        password: "1234",
+        database: "dbweek3",
+    })
+
+    try {
+        await connection.execute("DELETE FROM account_changes")
+        await connection.execute("DELETE FROM account")
+
+        await connection.execute(
+            `
+        INSERT INTO account (account_number, balance)
+        VALUES
+            (101, 5000.00),
+            (102, 2000.00),
+            (103, 3000.00)
+        `
+        )
+
+        await connection.execute(
+            `
+            INSERT INTO account_changes (account_number, amount, remark)
+            VALUES
+                (101, 5000.00, 'Initial deposit'),
+                (102, 2000.00, 'Initial deposit'),
+                (103, 3000.00, 'Initial deposit')
+        `
+        )
+
+        console.log("Sample data inserted into 'account' and 'account_changes'.")
+    } catch (err) {
+        console.error("Error inserting sample data:", err)
+    } finally {
+        await connection.end()
+    }
+}
+
+main().catch((err) => {
+    console.error(err)
+    process.exit(1)
+})
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