Relational Databases

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>What Is a Relational Database?</title>
<style>
.infographic-relationaldb {
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  background: var(--paper);
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.infographic-relationaldb[data-theme="dark"] {
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  --good:       #4ade80;
  --good-soft:  #123420;
  --on-accent:  #101418;
}
.infographic-relationaldb * { box-sizing: border-box; }

.rd-head { text-align: center; margin-bottom: 0.25rem; }
.rd-head h2 {
  font-family: var(--display-font);
  font-size: 2rem;
  margin: 0 0 0.5rem;
}
.rd-head p {
  color: var(--ink-soft);
  font-size: 1rem;
  margin: 0 auto;
  max-width: 600px;
  line-height: 1.55;
}

/* ---- Part A: chaos to order ---- */
.rd-frame {
  background: var(--paper-alt);
  border: 1px solid var(--line);
  border-radius: 10px;
  padding: 1.25rem;
  margin-top: 1.75rem;
}
.rd-frame-title { font-family: var(--display-font); font-size: 1.05rem; margin: 0 0 0.4rem; text-align: center; }
.rd-frame-desc { font-size: 0.87rem; color: var(--ink-soft); line-height: 1.5; margin: 0 0 1rem; text-align: center; }

.rd-chaos-scroll { overflow-x: auto; -webkit-overflow-scrolling: touch; }
.rd-chaos-stage {
  position: relative;
  height: 260px;
  min-width: 460px;
  background: var(--paper);
  border: 1px dashed var(--line);
  border-radius: 8px;
  overflow: hidden;
}
.rd-chaos-stage.is-organized { border-style: solid; border-color: var(--accent); }

.rd-grid-lines { position: absolute; inset: 0; opacity: 0; transition: opacity 0.4s; pointer-events: none; }
.rd-chaos-stage.is-organized .rd-grid-lines { opacity: 1; }
.rd-grid-line { position: absolute; background: var(--line); }

.rd-header-row { position: absolute; display: flex; opacity: 0; transition: opacity 0.4s 0.6s; pointer-events: none; }
.rd-chaos-stage.is-organized .rd-header-row { opacity: 1; }
.rd-header-cell {
  width: 130px;
  font-size: 0.7rem;
  font-weight: 700;
  color: var(--on-accent);
  background: var(--accent);
  padding: 0.3rem 0.5rem;
  text-align: center;
}

.rd-chip {
  position: absolute;
  background: var(--accent-soft);
  color: var(--accent);
  border: 1px solid var(--accent);
  border-radius: 6px;
  padding: 0.35rem 0.6rem;
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  font-size: 0.78rem;
  font-weight: 600;
  width: 110px;
  text-align: center;
  animation: rd-float 3.2s ease-in-out infinite;
  transition: left 0.7s cubic-bezier(.34,1.4,.64,1), top 0.7s cubic-bezier(.34,1.4,.64,1), transform 0.7s ease, border-radius 0.4s;
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.rd-chaos-stage.is-organized .rd-chip {
  animation: none;
  border-radius: 0;
  background: var(--paper);
  color: var(--ink);
  border-color: var(--line);
}
@keyframes rd-float {
  0%, 100% { margin-top: 0px; }
  50% { margin-top: -8px; }
}

.rd-organize-row { display: flex; justify-content: center; gap: 0.6rem; margin-top: 1.1rem; }
.rd-organize-btn {
  font: inherit;
  font-size: 0.88rem;
  background: var(--accent);
  color: var(--on-accent);
  border: none;
  border-radius: 7px;
  padding: 0.6rem 1.3rem;
  cursor: pointer;
}
.rd-organize-btn:hover { opacity: 0.9; }
.rd-organize-btn:disabled { opacity: 0.4; cursor: not-allowed; }
.rd-reset-mini-btn {
  font: inherit;
  font-size: 0.82rem;
  background: var(--paper);
  border: 1px solid var(--line);
  border-radius: 7px;
  padding: 0.6rem 1rem;
  cursor: pointer;
  color: var(--ink);
  display: none;
}
.rd-reset-mini-btn.is-visible { display: inline-block; }
.rd-reset-mini-btn:hover { border-color: var(--accent); }

.rd-reveal-line {
  text-align: center;
  font-size: 0.9rem;
  color: var(--good);
  margin-top: 1rem;
  opacity: 0;
  transition: opacity 0.5s 1s;
}
.rd-reveal-line.is-visible { opacity: 1; }

/* ---- Part B: connected tables ---- */
.rd-tables-row {
  display: flex;
  align-items: center;
  gap: 0;
  margin-top: 0.5rem;
  min-width: 0;
}
.rd-table-scroll-wrap { flex: 1; min-width: 0; overflow-x: auto; }
table.rd-table {
  width: 100%;
  min-width: 150px;
  border-collapse: collapse;
  background: var(--paper);
  border-radius: 8px;
  font-size: 0.8rem;
}
table.rd-table th, table.rd-table td {
  border: 1px solid var(--line);
  padding: 0.4rem 0.55rem;
  text-align: left;
  white-space: nowrap;
  transition: background 0.2s, color 0.2s;
}
table.rd-table th { background: var(--accent); color: var(--on-accent); font-weight: 700; font-size: 0.7rem; }
table.rd-table tbody tr { cursor: pointer; }
table.rd-table tr.is-linked td { background: var(--accent-soft); color: var(--accent); font-weight: 700; }

.rd-connector {
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  height: 3px;
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  background-size: 24px 3px;
  animation: rd-flow 0.8s linear infinite;
}
@keyframes rd-flow { from { background-position-x: 0; } to { background-position-x: -24px; } }

.rd-table-name { font-size: 0.75rem; color: var(--ink-soft); text-align: center; margin: 0 0 0.4rem; }

@media (max-width: 700px) {
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  .rd-table-scroll-wrap { width: 100%; align-self: stretch; -webkit-overflow-scrolling: touch; }
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  @keyframes rd-flow-v { from { background-position-y: 0; } to { background-position-y: -24px; } }
}

@media (prefers-reduced-motion: reduce) {
  .infographic-relationaldb *, .infographic-relationaldb *::before, .infographic-relationaldb *::after {
    transition-duration: 0.001ms !important;
    animation-duration: 0.001ms !important;
  }
}
</style>
</head>
<body>

<div class="infographic-relationaldb" id="relationaldb">

  <div class="rd-head">
    <h2>What Is a Relational Database?</h2>
    <p>Loose facts scattered everywhere become useful once they're organized into rows and columns — and linked together by shared keys.</p>
  </div>

  <div class="rd-frame">
    <p class="rd-frame-title">From chaos to structure</p>
    <p class="rd-frame-desc">This is raw, unorganized data about students. Watch what "relational" actually means.</p>

    <div class="rd-chaos-scroll">
      <div class="rd-chaos-stage" id="rdStage">
        <div class="rd-grid-lines" id="rdGridLines"></div>
        <div class="rd-header-row" id="rdHeaderRow" style="left:30px; top:16px;">
          <div class="rd-header-cell">StudentID</div>
          <div class="rd-header-cell">Name</div>
          <div class="rd-header-cell">Age</div>
        </div>
        <!-- chips injected by JS -->
      </div>
    </div>

    <div class="rd-organize-row">
      <button class="rd-organize-btn" id="rdOrganizeBtn" type="button">🔀 Organize the data</button>
      <button class="rd-reset-mini-btn" id="rdChaosReset" type="button">↺ Scatter again</button>
    </div>
    <p class="rd-reveal-line" id="rdRevealLine">✔️ That's it — a table is just organized data. "Relational" is what happens next: linking tables like this one together.</p>
  </div>

  <div class="rd-frame">
    <p class="rd-frame-title">Tables, linked by keys</p>
    <p class="rd-frame-desc">Click a Student to see exactly which Enrollment and Course rows connect to them.</p>

    <div class="rd-tables-row">
      <div class="rd-table-scroll-wrap">
        <p class="rd-table-name">Students</p>
        <table class="rd-table" id="rdStudents">
          <thead><tr><th>ID</th><th>Name</th></tr></thead>
          <tbody>
            <tr data-student="101"><td>101</td><td>Alice</td></tr>
            <tr data-student="102"><td>102</td><td>Bob</td></tr>
          </tbody>
        </table>
      </div>
      <div class="rd-connector"></div>
      <div class="rd-table-scroll-wrap">
        <p class="rd-table-name">Enrollment</p>
        <table class="rd-table" id="rdEnrollment">
          <thead><tr><th>SID</th><th>CID</th></tr></thead>
          <tbody>
            <tr data-student="101" data-course="C1"><td>101</td><td>C1</td></tr>
            <tr data-student="102" data-course="C2"><td>102</td><td>C2</td></tr>
          </tbody>
        </table>
      </div>
      <div class="rd-connector"></div>
      <div class="rd-table-scroll-wrap">
        <p class="rd-table-name">Courses</p>
        <table class="rd-table" id="rdCourses">
          <thead><tr><th>ID</th><th>Name</th></tr></thead>
          <tbody>
            <tr data-course="C1"><td>C1</td><td>Math</td></tr>
            <tr data-course="C2"><td>C2</td><td>Physics</td></tr>
          </tbody>
        </table>
      </div>
    </div>
  </div>

</div>

<script>
(function () {
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    dark = match ? match[1] === 'true' : false;
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  if (dark) wrapper.setAttribute('data-theme', 'dark');
})();

/* ---- Part A: chaos to order ---- */
(function () {
  const stage = document.getElementById('rdStage');
  const organizeBtn = document.getElementById('rdOrganizeBtn');
  const chaosReset = document.getElementById('rdChaosReset');
  const revealLine = document.getElementById('rdRevealLine');
  const gridLines = document.getElementById('rdGridLines');

  const data = [
    ['101', 'Alice', '24'],
    ['102', 'Bob', '22'],
    ['103', 'Carol', '26']
  ];

  const colX = [30, 160, 290];
  const rowY = [56, 100, 144];
  let chips = [];

  function randomPos() {
    const stageW = stage.clientWidth || 600;
    const stageH = 260;
    return {
      left: Math.random() * (stageW - 130) + 5,
      top: Math.random() * (stageH - 100) + 60,
      rot: (Math.random() * 30 - 15).toFixed(1)
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    data.forEach((row, r) => {
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        const chip = document.createElement('div');
        chip.className = 'rd-chip';
        chip.textContent = val;
        const pos = randomPos();
        chip.style.left = pos.left + 'px';
        chip.style.top = pos.top + 'px';
        chip.style.transform = 'rotate(' + pos.rot + 'deg)';
        chip.style.animationDelay = (Math.random() * 2) + 's';
        stage.appendChild(chip);
        chips.push({ el: chip, row: r, col: c });
      });
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  }

  function buildGridLines() {
    gridLines.innerHTML = '';
    for (let r = 0; r <= 3; r++) {
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      line.className = 'rd-grid-line';
      line.style.left = '28px';
      line.style.right = '20px';
      line.style.top = (48 + r * 44) + 'px';
      line.style.height = '1px';
      gridLines.appendChild(line);
    }
  }
  buildGridLines();
  buildChips();

  organizeBtn.addEventListener('click', () => {
    organizeBtn.disabled = true;
    chips.forEach((chip, i) => {
      setTimeout(() => {
        chip.el.style.left = colX[chip.col] + 'px';
        chip.el.style.top = rowY[chip.row] + 'px';
        chip.el.style.transform = 'rotate(0deg)';
      }, i * 90);
    });
    setTimeout(() => {
      stage.classList.add('is-organized');
      revealLine.classList.add('is-visible');
      chaosReset.classList.add('is-visible');
    }, chips.length * 90 + 300);
  });

  chaosReset.addEventListener('click', () => {
    stage.classList.remove('is-organized');
    revealLine.classList.remove('is-visible');
    chaosReset.classList.remove('is-visible');
    organizeBtn.disabled = false;
    buildChips();
  });
})();

/* ---- Part B: linked tables ---- */
(function () {
  const studentsTable = document.getElementById('rdStudents');
  const enrollmentTable = document.getElementById('rdEnrollment');
  const coursesTable = document.getElementById('rdCourses');

  function clearLinks() {
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      t.querySelectorAll('tbody tr').forEach(tr => tr.classList.remove('is-linked'));
    });
  }

  studentsTable.querySelectorAll('tbody tr').forEach(row => {
    row.addEventListener('click', () => {
      const wasLinked = row.classList.contains('is-linked');
      clearLinks();
      if (wasLinked) return;
      const sid = row.dataset.student;
      row.classList.add('is-linked');
      enrollmentTable.querySelectorAll('tbody tr').forEach(eRow => {
        if (eRow.dataset.student === sid) {
          eRow.classList.add('is-linked');
          const cid = eRow.dataset.course;
          coursesTable.querySelectorAll('tbody tr').forEach(cRow => {
            if (cRow.dataset.course === cid) cRow.classList.add('is-linked');
          });
        }
      });
    });
  });
})();
</script>

</body>
</html>

.demo {
  font-family: system-ui, sans-serif;
  padding: 16px;
}

.demo h1 {
  color: #2563eb;
  margin: 0 0 8px;
}

.demo p {
  color: #4b5563;
  margin: 0;
}

document.querySelector('.demo h1')?.addEventListener('click', () => {
  alert('Hello from live preview!');
});