Hanna melnyk w2 databases

.gitignore

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

Week1/.gitignore

@@ -1,3 +1,6 @@
 package.json
 package-lock.json
-create-table.js
+create-table.js
+
+
+Week1/node_modules/

Week1/exercise_1.js

@@ -0,0 +1,76 @@
+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

@@ -0,0 +1,44 @@
+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

@@ -0,0 +1,29 @@
+//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

@@ -0,0 +1,99 @@
+//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();
+