Alaa_Nahser-w3-databases

Week3/homework/SQL-Normalization/sqlNormalization.md

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+### 1. Columns that violate 1NF
+
+- **dinner_date**: values use different formats, so the column does not have one consistent domain.
+- **food_code**: contains multiple values in a single cell (not atomic).
+- **food_description**: contains multiple values in a single cell (not atomic).
+
+### 2. Entities that can be extracted
+
+- Member
+- Dinner
+- Venue
+- Food
+
+### 3. 3NF-compliant tables and columns (no junction tables)
+
+#### Member
+
+- member_id (PK)
+- member_name
+- member_address
+
+#### Dinner
+
+- dinner_id (PK)
+- dinner_date
+- venue_code (FK → Venue.venue_code)
+
+#### Venue
+
+- venue_code (PK)
+- venue_description
+
+#### Food
+
+- food_code (PK)
+- food_description

Week3/homework/SQL-Transactions/client.js

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+import { Client } from "pg";
+
+const config = {
+  host: "localhost",
+  user: "hyfuser",
+  password: "hyfpass",
+  database: "postgres",
+  port: 5432,
+};
+
+const client = new Client(config);
+export default client;

Week3/homework/SQL-Transactions/docker-compose.yml

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+version: "3.9"
+
+services:
+  postgres:
+    image: postgres:16
+    container_name: postgres-db
+    environment:
+      POSTGRES_USER: hyfuser
+      POSTGRES_PASSWORD: hyfpass
+      POSTGRES_DB: postgres
+    ports:
+      - "5432:5432"
+    volumes:
+      - postgres_data:/var/lib/postgresql/data
+
+volumes:
+  postgres_data:

Week3/homework/SQL-Transactions/package.json

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+{
+  "name": "sql-transactions",
+  "version": "1.0.0",
+  "main": "client.js",
+  "type": "module",
+  "scripts": {
+    "test": "echo \"Error: no test specified\" && exit 1"
+  },
+  "keywords": [],
+  "author": "",
+  "license": "ISC",
+  "description": "",
+  "dependencies": {
+    "pg": "^8.16.3"
+  }
+}

Week3/homework/SQL-Transactions/transaction.js

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+import client from "./client.js";
+
+async function runTransaction() {
+  try {
+    await client.connect();
+    console.log("Connected to PostgreSQL database!");
+
+    await client.query("BEGIN");
+
+    //withdraw 1000 from account 101
+    await client.query(
+      `UPDATE account SET balance = balance - 1000 WHERE account_number = 101`
+    );
+
+    //Deposit the money to 102
+    await client.query(`
+      UPDATE account SET balance = balance + 1000 WHERE account_number = 102
+    `);
+
+    //log them to account changes
+    await client.query(`
+  INSERT INTO account_changes (account_number, amount, changed_date, remark) 
+  VALUES 
+    (101, -1000.00, NOW(), 'Transfer 1000 to 102'),
+    (102,  1000.00, NOW(), '1000 from 101')
+`);
+
+    await client.query("COMMIT");
+
+    // if successful
+    console.log("Transaction executed successfully");
+  } catch (error) {
+    console.error("Error executing transaction", error);
+    await client.query("ROLLBACK");
+  } finally {
+    await client.end();
+  }
+}
+
+runTransaction();

Week3/homework/SQL-Transactions/transactions-create-tables.js

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+import client from "./client.js";
+
+async function seedDatabase() {
+  try {
+    await client.connect();
+    console.log("Connected to PostgreSQL database!");
+
+    await client.query("BEGIN");
+
+    await client.query("DROP TABLE IF EXISTS account_changes");
+
+    await client.query("DROP TABLE IF EXISTS account");
+
+    await client.query(`CREATE TABLE account (
+	account_number INTEGER NOT NULL PRIMARY KEY,
+	balance NUMERIC(12,2)
+        )`);
+
+    await client.query(`CREATE TABLE account_changes (
+	change_number SERIAL PRIMARY KEY,
+	account_number INTEGER, 
+	amount NUMERIC(12,2),
+	changed_date TIMESTAMP,
+	remark VARCHAR(250),
+	FOREIGN KEY (account_number) REFERENCES account(account_number)
+)`);
+
+    await client.query("COMMIT");
+
+    // if successful
+    console.log("Tables created successfully");
+  } catch (error) {
+    console.error("Error seeding database:", error);
+    await client.query("ROLLBACK");
+    console.log("Transaction failed");
+  } finally {
+    await client.end();
+  }
+}
+
+seedDatabase();

Week3/homework/SQL-Transactions/transactions-insert-values.js

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+import client from "./client.js";
+
+async function insertValues() {
+  try {
+    await client.connect();
+    console.log("Connected to PostgreSQL database!");
+
+    await client.query("BEGIN");
+
+    await client.query(`INSERT INTO account (account_number, balance) VALUES
+    (101, 2000.00),
+    (102, 500.00),
+    (103, 300.00),
+    (104, 50.00),
+    (105, 0.00)`);
+
+    await client.query(`INSERT INTO account_changes(account_number, amount, changed_date, remark) VALUES
+    (101, 200.00, '2025-01-20T10:15:00Z', 'Deposit'),
+    (102, -50.00, '2025-01-21T14:30:00Z', 'ATM Withdrawal'),
+    (103, 1000.00, '2025-01-22T09:00:00Z', 'Salary Deposit'),
+    (101, -100.00, '2025-01-23T11:45:00Z', 'Online Purchase'),
+    (101, 200.00, '2025-01-24T10:15:00Z', 'ATM Withdrawal')
+    `);
+
+    await client.query("COMMIT");
+
+    // if successful
+    console.log("Tables inserted successfully");
+  } catch (error) {
+    console.error("Error inserting tables", error);
+    await client.query("ROLLBACK");
+  } finally {
+    await client.end();
+  }
+}
+
+insertValues();