Vlad-2week-DB

Week2/scripts/ex3_1_keys.js

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+// ex3_1_keys.js
+// Week2 – Exercise 3.1 (Keys)
+// Creates DB "research", table authors, and adds self-referencing FK "mentor".
+
+import dotenv from "dotenv";
+import pg from "pg";
+dotenv.config();
+
+const { Client } = pg;
+
+const DB_NAME = "research";
+
+const admin = new Client({
+  host: process.env.PGHOST,
+  port: process.env.PGPORT,
+  user: process.env.PGUSER,
+  password: process.env.PGPASSWORD,
+  database: "postgres",
+});
+
+const research = (dbName = DB_NAME) =>
+  new Client({
+    host: process.env.PGHOST,
+    port: process.env.PGPORT,
+    user: process.env.PGUSER,
+    password: process.env.PGPASSWORD,
+    database: dbName,
+  });
+
+async function run() {
+  let root, db;
+  try {
+    // 1) Create DB "research" fresh (idempotent)
+    root = admin;
+    await root.connect();
+    await root.query(
+      `SELECT pg_terminate_backend(pid)
+                      FROM pg_stat_activity
+                      WHERE datname = $1 AND pid <> pg_backend_pid();`,
+      [DB_NAME]
+    );
+    await root.query(`DROP DATABASE IF EXISTS ${DB_NAME};`);
+    await root.query(`CREATE DATABASE ${DB_NAME};`);
+    await root.end();
+    root = null;
+
+    // 2) Connect to research and create authors
+    db = research();
+    await db.connect();
+
+    await db.query(`
+      CREATE TABLE authors (
+        author_id     INTEGER GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
+        author_name   TEXT    NOT NULL,
+        university    TEXT    NOT NULL,
+        date_of_birth DATE,
+        h_index       SMALLINT CHECK (h_index >= 0),
+        gender        TEXT CHECK (gender IN ('male','female','nonbinary','other'))
+      );
+    `);
+
+    // 3) Add mentor column that references authors.author_id (self FK)
+    await db.query(`
+      ALTER TABLE authors
+      ADD COLUMN mentor INTEGER NULL;
+    `);
+
+    await db.query(`
+      ALTER TABLE authors
+      ADD CONSTRAINT fk_authors_mentor
+      FOREIGN KEY (mentor) REFERENCES authors(author_id)
+      ON DELETE SET NULL;
+    `);
+
+    console.log(" ex3_1_keys: authors created, mentor FK added");
+  } catch (e) {
+    console.error(" ex3_1_keys failed:", e);
+    process.exitCode = 1;
+  } finally {
+    if (root) {
+      try {
+        await root.end();
+      } catch {}
+    }
+    if (db) {
+      try {
+        await db.end();
+      } catch {}
+    }
+  }
+}
+run();

Week2/scripts/ex3_2_relationships.js

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+// ex3_2_relationships.js
+// Week2 – Exercise 3.2 (Relationships)
+// Adds research_papers, author_papers; inserts 15 authors, 30 papers, and links.
+
+import dotenv from "dotenv";
+import pg from "pg";
+dotenv.config();
+
+const { Client } = pg;
+
+const DB_NAME = "research";
+const db = new Client({
+  host: process.env.PGHOST,
+  port: process.env.PGPORT,
+  user: process.env.PGUSER,
+  password: process.env.PGPASSWORD,
+  database: DB_NAME,
+});
+
+async function run() {
+  try {
+    await db.connect();
+
+    // 1) Tables for papers and m:n link
+    await db.query(`
+      CREATE TABLE IF NOT EXISTS research_papers (
+        paper_id     INTEGER GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
+        paper_title  TEXT NOT NULL UNIQUE,
+        conference   TEXT,
+        publish_date DATE
+      );
+    `);
+
+    await db.query(`
+      CREATE TABLE IF NOT EXISTS author_papers (
+        author_id INTEGER NOT NULL REFERENCES authors(author_id) ON DELETE CASCADE,
+        paper_id  INTEGER NOT NULL REFERENCES research_papers(paper_id) ON DELETE CASCADE,
+        PRIMARY KEY (author_id, paper_id)
+      );
+    `);
+
+    // 2) Seed 15 authors (some mentors set later)
+    const authors = [
+      ["Alice Kim", "TU Delft", "1988-03-01", 12, "female"],
+      ["Bob Ivanov", "UvA", "1985-06-10", 18, "male"],
+      ["Carla Gomez", "VU", "1990-12-01", 9, "female"],
+      ["Dmitri Petrov", "TU Delft", "1982-07-22", 22, "male"],
+      ["Eve Tan", "Leiden", "1991-09-19", 7, "female"],
+      ["Felix Zhou", "TU/e", "1986-01-05", 15, "male"],
+      ["Gina Rossi", "UvA", "1992-04-14", 6, "female"],
+      ["Hiro Sato", "TU Delft", "1984-11-08", 24, "male"],
+      ["Ivy Wang", "Leiden", "1993-02-17", 5, "female"],
+      ["Jamal Noor", "VU", "1987-08-03", 11, "male"],
+      ["Kira Novak", "UvA", "1990-01-29", 8, "female"],
+      ["Leo Martins", "TU/e", "1983-03-13", 19, "male"],
+      ["Mina Park", "Leiden", "1994-04-04", 4, "female"],
+      ["Nate Quinn", "TU Delft", "1989-06-06", 13, "male"],
+      ["Ola Berg", "VU", "1985-10-10", 17, "male"],
+    ];
+
+    await db.query(`TRUNCATE authors RESTART IDENTITY CASCADE;`);
+    for (const a of authors) {
+      await db.query(
+        `INSERT INTO authors(author_name,university,date_of_birth,h_index,gender)
+         VALUES ($1,$2,$3,$4,$5);`,
+        a
+      );
+    }
+
+    await db.query(
+      `UPDATE authors SET mentor = 4  WHERE author_id IN (1,3,5);`
+    );
+    await db.query(
+      `UPDATE authors SET mentor = 8  WHERE author_id IN (2,6,7);`
+    );
+    await db.query(
+      `UPDATE authors SET mentor = 12 WHERE author_id IN (9,10,11);`
+    );
+    await db.query(
+      `UPDATE authors SET mentor = 4  WHERE author_id IN (13,14,15);`
+    );
+
+    // 3) Seed 30 papers
+    await db.query(`TRUNCATE research_papers RESTART IDENTITY CASCADE;`);
+    const confs = ["ICDB", "SIGMOD", "VLDB", "ICDE", "EDBT"];
+    const today = new Date();
+
+    for (let i = 1; i <= 30; i++) {
+      const title = `On Relational Patterns ${i}`;
+      const conf = confs[i % confs.length];
+      const date = new Date(today.getFullYear() - (i % 8), i % 12, (i % 28) + 1)
+        .toISOString()
+        .slice(0, 10);
+      await db.query(
+        `INSERT INTO research_papers(paper_title,conference,publish_date)
+         VALUES ($1,$2,$3);`,
+        [title, conf, date]
+      );
+    }
+
+    // 4) Link authors to papers
+    await db.query(`TRUNCATE author_papers;`);
+    for (let paperId = 1; paperId <= 30; paperId++) {
+      const a1 = ((paperId + 0) % 15) + 1;
+      const a2 = ((paperId + 3) % 15) + 1;
+      const a3 = ((paperId + 7) % 15) + 1;
+      const pick = new Set([a1, a2, ...(paperId % 3 === 0 ? [a3] : [])]);
+      for (const aid of pick) {
+        await db.query(
+          `INSERT INTO author_papers(author_id,paper_id)
+           VALUES ($1,$2) ON CONFLICT DO NOTHING;`,
+          [aid, paperId]
+        );
+      }
+    }
+
+    console.log(" ex3_2_relationships: papers, links, and seed inserted");
+  } catch (e) {
+    console.error(" ex3_2_relationships failed:", e);
+    process.exitCode = 1;
+  } finally {
+    try {
+      await db.end();
+    } catch {}
+  }
+}
+run();

Week2/scripts/ex3_3_joins.js

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+// ex3_3_joins.js
+// Week2 – Exercise 3.3 (Joins)
+
+import dotenv from "dotenv";
+import pg from "pg";
+dotenv.config();
+
+const { Client } = pg;
+
+const db = new Client({
+  host: process.env.PGHOST,
+  port: process.env.PGPORT,
+  user: process.env.PGUSER,
+  password: process.env.PGPASSWORD,
+  database: "research",
+});
+
+async function q(label, sql, params = []) {
+  const res = await db.query(sql, params);
+  console.log(`\n=== ${label} ===`);
+  console.table(res.rows.slice(0, 15));
+}
+
+async function run() {
+  try {
+    await db.connect();
+
+    // 1) names of all authors and their mentors
+    await q(
+      "Authors and their mentors",
+      `SELECT a.author_name AS author, m.author_name AS mentor
+       FROM authors a
+       LEFT JOIN authors m ON a.mentor = m.author_id
+       ORDER BY author;`
+    );
+
+    // 2) all columns of authors and their published paper_title
+    //    include authors without papers
+    await q(
+      "Authors and their papers (include authors without papers)",
+      `SELECT a.*, rp.paper_title
+       FROM authors a
+       LEFT JOIN author_papers ap ON ap.author_id = a.author_id
+       LEFT JOIN research_papers rp ON rp.paper_id = ap.paper_id
+       ORDER BY a.author_id, rp.paper_title NULLS LAST;`
+    );
+
+    console.log("\n ex3_3_joins: done");
+  } catch (e) {
+    console.error(" ex3_3_joins failed:", e);
+    process.exitCode = 1;
+  } finally {
+    try {
+      await db.end();
+    } catch {}
+  }
+}
+run();

Week2/scripts/ex3_4_aggregates.js

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+// ex3_4_aggregates.js
+// Week2 – Exercise 3.4 (Aggregate Functions)
+
+import dotenv from "dotenv";
+import pg from "pg";
+dotenv.config();
+
+const { Client } = pg;
+
+const db = new Client({
+  host: process.env.PGHOST,
+  port: process.env.PGPORT,
+  user: process.env.PGUSER,
+  password: process.env.PGPASSWORD,
+  database: "research",
+});
+
+async function q(label, sql, params = []) {
+  const res = await db.query(sql, params);
+  console.log(`\n=== ${label} ===`);
+  console.table(res.rows.slice(0, 20));
+}
+
+async function run() {
+  try {
+    await db.connect();
+
+    // 1) All research papers and the number of authors that wrote that paper
+    await q(
+      "Paper → number of authors",
+      `SELECT rp.paper_title, COUNT(ap.author_id) AS authors_count
+       FROM research_papers rp
+       LEFT JOIN author_papers ap ON ap.paper_id = rp.paper_id
+       GROUP BY rp.paper_id, rp.paper_title
+       ORDER BY authors_count DESC, rp.paper_title;`
+    );
+
+    // 2) Sum of the research papers published by all female authors
+    await q(
+      "Total papers by female authors",
+      `SELECT SUM(cnt) AS total_papers_by_female
+       FROM (
+         SELECT a.author_id, COUNT(ap.paper_id) AS cnt
+         FROM authors a
+         LEFT JOIN author_papers ap ON ap.author_id = a.author_id
+         WHERE a.gender = 'female'
+         GROUP BY a.author_id
+       ) x;`
+    );
+
+    // 3) Average of the h-index of all authors per university
+    await q(
+      "Average h-index per university",
+      `SELECT university, ROUND(AVG(h_index)::numeric, 2) AS avg_h_index
+       FROM authors
+       GROUP BY university
+       ORDER BY university;`
+    );
+
+    // 4) Sum of the research papers of the authors per university
+    await q(
+      "Sum of papers per university",
+      `SELECT a.university, COUNT(ap.paper_id) AS papers_sum
+       FROM authors a
+       LEFT JOIN author_papers ap ON ap.author_id = a.author_id
+       GROUP BY a.university
+       ORDER BY papers_sum DESC, a.university;`
+    );
+
+    // 5) Min/Max h-index per university
+    await q(
+      "Min/Max h-index per university",
+      `SELECT university,
+              MIN(h_index) AS min_h,
+              MAX(h_index) AS max_h
+       FROM authors
+       GROUP BY university
+       ORDER BY university;`
+    );
+
+    console.log("\n ex3_4_aggregates: done");
+  } catch (e) {
+    console.error(" ex3_4_aggregates failed:", e);
+    process.exitCode = 1;
+  } finally {
+    try {
+      await db.end();
+    } catch {}
+  }
+}
+run();