Hanna melnyk w2 databases

.gitignore

@@ -1,4 +1,6 @@
 node_modules/
+/*/.env
+*/node_modules
 */node_modules/
 **/*.DS_Store
 **/*-secret.json

Week1/.gitignore

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 package.json
 package-lock.json
-create-table.js
+create-table.js
+
+
+Week1/node_modules/

Week1/exercise_1.js

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+const mysql = require('mysql');
+
+const connection = mysql.createConnection({
+ host: 'localhost',
+ user: 'hyfuser',
+ password: 'hyfpassword',
+ multipleStatements: true
+});
+
+
+/*Connect to SQL server*/
+connection.connect(err => {
+ if (err) {
+ return console.error('Connection error: ' + err.stack);
+ }
+ console.log('Connected!');
+});
+
+
+/*SQL queries*/
+const createDatabaseAndTables =
+ `DROP DATABASE IF EXISTS meetup;
+ CREATE DATABASE meetup;
+ USE meetup;
+
+ CREATE TABLE Invitee (
+ invitee_no INT AUTO_INCREMENT PRIMARY KEY,
+ invitee_name VARCHAR(100),
+ invited_by VARCHAR(100)
+ );
+
+ CREATE TABLE Room (
+ room_no INT AUTO_INCREMENT PRIMARY KEY,
+ room_name VARCHAR(50),
+ floor_number INT
+ );
+
+ CREATE TABLE Meeting (
+ meeting_no INT AUTO_INCREMENT PRIMARY KEY,
+ meeting_title VARCHAR(100),
+ starting_time DATETIME,
+ ending_time DATETIME,
+ room_no INT,
+ FOREIGN KEY (room_no) REFERENCES Room(room_no)
+ );
+
+ INSERT INTO Room (room_name, floor_number) VALUES
+ ('Paris', 1),
+ ('New York', 2),
+ ('Tokyo', 3),
+ ('London', 4),
+ ('Berlin', 5);
+
+ INSERT INTO Invitee (invitee_name, invited_by) VALUES
+ ('Victor Hugo', 'Alexandre Dumas'),
+ ('Mark Twain', 'Henry James'),
+ ('Haruki Murakami', 'Kenzaburo Oe'),
+ ('Charles Dickens', 'Wilkie Collins'),
+ ('Albert Einstein', 'Niels Bohr');
+
+ INSERT INTO Meeting (meeting_title, starting_time, ending_time, room_no) VALUES
+ ('Literary Classics Discussion', '2024-08-01 09:00:00', '2024-08-01 10:00:00', 1),
+ ('American Literature Seminar', '2024-08-02 11:00:00', '2024-08-02 12:00:00', 2),
+ ('Japanese Fiction Workshop', '2024-08-03 14:00:00', '2024-08-03 15:00:00', 3),
+ ('Victorian Literature Symposium', '2024-08-04 16:00:00', '2024-08-04 17:00:00', 4),
+ ('Scientific Innovations Forum', '2024-08-05 13:00:00', '2024-08-05 14:00:00', 5);`;
+
+
+// Execute the queries
+connection.query(createDatabaseAndTables, (error, results, fields) => {
+ if (error) throw error;
+ console.log('Database and tables created, and data inserted');
+});
+
+// Close the connection
+connection.end();

Week1/exercise_2.js

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+const mysql = require('mysql');
+
+const connection = mysql.createConnection({
+ host: 'localhost',
+ user: 'hyfuser',
+ password: 'hyfpassword',
+ database: 'world'
+});
+
+/*Connect to SQL server*/
+connection.connect(err => {
+ if (err) {
+ return console.error('Connection error: ' + err.stack);
+ }
+ console.log('Connected!');
+});
+
+
+// Queries
+const queries = [
+ "SELECT Name FROM country WHERE Population > 8000000;",
+ "SELECT Name FROM country WHERE Name LIKE '%land%';",
+ "SELECT Name FROM city WHERE Population BETWEEN 500000 AND 1000000;",
+ "SELECT Name FROM country WHERE Continent = 'Europe';",
+ "SELECT Name FROM country ORDER BY SurfaceArea DESC;",
+ "SELECT Name FROM city WHERE CountryCode = 'NLD';",
+ "SELECT Population FROM city WHERE Name = 'Rotterdam';",
+ "SELECT Name FROM country ORDER BY SurfaceArea DESC LIMIT 10;",
+ "SELECT Name FROM city ORDER BY Population DESC LIMIT 10;",
+ "SELECT SUM(Population) AS WorldPopulation FROM country;"
+];
+
+
+// Execute each query
+queries.forEach((query, index) => {
+ connection.query(query, (error, results) => {
+ if (error) throw error;
+ console.log(`Query ${index + 1}:`);
+ console.log(results);
+ });
+});
+
+// End the connection
+connection.end();

Week2/connection_query.js

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+//C:\Users\knowl\Documents\hyf\databases\Week2\connection_query.js
+import mysql from 'mysql';
+
+export const createNewConnection = () => {
+ return mysql.createConnection({
+ host: 'localhost',
+ user: 'hyfuser',
+ password: 'hyfpassword',
+ multipleStatements: true,
+ });
+};
+
+export const useDatabase = (connection) => {
+ return new Promise((resolve, reject) => {
+ const createDatabaseAndUse = `
+ CREATE DATABASE IF NOT EXISTS w2_research;
+ USE w2_research;
+ `;
+ connection.query(createDatabaseAndUse, (err, results) => {
+ if (err) {
+ console.error('Error creating or selecting database:', err.stack);
+ reject(err);
+ return;
+ }
+ console.log('Database selected successfully.');
+ resolve();
+ });
+ });
+};

Week2/exercise_1.js

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+//C:\Users\knowl\Documents\hyf\databases\Week2\exercise_1.js
+import {createNewConnection, useDatabase} from './connection_query.js';
+
+
+const createAuthorsTable = (connection) => {
+ return new Promise((resolve, reject) => {
+ const createAuthorsTableQuery = `
+ CREATE TABLE IF NOT EXISTS authors (
+ author_id INT AUTO_INCREMENT PRIMARY KEY,
+ author_name VARCHAR(100) NOT NULL,
+ university VARCHAR(100),
+ date_of_birth DATE,
+ h_index INT,
+ gender ENUM('Male', 'Female', 'Other')
+ );
+ `;
+ connection.query(createAuthorsTableQuery, (err, results) => {
+ if (err) {
+ console.error('Error creating authors table:', err.stack);
+ reject(err);
+ return;
+ }
+ console.log('Authors table created.');
+ resolve();
+ });
+ });
+};
+
+const addMentorColumn = (connection) => {
+ return new Promise((resolve, reject) => {
+ const checkColumnExistsQuery = `
+ SELECT COUNT(*) AS columnExists
+ FROM information_schema.columns
+ WHERE table_name = 'authors'
+ AND column_name = 'mentor';
+ `;
+
+ connection.query(checkColumnExistsQuery, (err, results) => {
+ if (err) {
+ console.error('Error checking for mentor column:', err.stack);
+ reject(err);
+ return;
+ }
+
+ const columnExists = results[0].columnExists;
+
+ if (columnExists) {
+ console.log('Mentor column already exists. No changes made.');
+ resolve();
+ } else {
+ const addMentorColumnQuery = `
+ ALTER TABLE authors 
+ ADD COLUMN mentor INT,
+ ADD CONSTRAINT fk_mentor
+ FOREIGN KEY (mentor) REFERENCES authors(author_id)
+ ON DELETE SET NULL
+ ON UPDATE CASCADE;
+ `;
+
+ connection.query(addMentorColumnQuery, (err, results) => {
+ if (err) {
+ console.error('Error adding mentor column:', err.stack);
+ reject(err);
+ return;
+ }
+ console.log('Mentor column added with foreign key constraint.');
+ resolve();
+ });
+ }
+ });
+ });
+};
+
+
+const exerciseOne = async () => {
+ const connection = createNewConnection();
+ connection.connect(err => {
+ if (err) {
+ return console.error('Connection error: ' + err.stack);
+ }
+ console.log('exercise_1: Connected!');
+ });
+
+
+ try {
+ await useDatabase(connection) ; // Select the database
+ await createAuthorsTable(connection) ; // Create the authors table
+ await addMentorColumn(connection) ; // Add the mentor column with foreign key
+
+ } catch (err) {
+ console.error('Failed to set up the database:', err);
+ } finally {
+ connection.end();
+ }
+};
+
+
+exerciseOne();
+