Three Schema Architecture | View of Data | Abstraction provided by DBMS

<div class="infographic-schema" id="schemaWrap">
  <style>
    .infographic-schema {
      --ink:        #1a1a1a;
      --ink-soft:   #5c5c5c;
      --paper:      #ffffff;
      --paper-alt:  #f6f3ee;
      --accent:     #2563eb;
      --accent-soft:#e3ebfd;
      --line:       #ddd6c9;
      --code-bg:    #1e2430;
      --code-ink:   #d7dde8;
      --tok-kw:     #7aa2f7;
      --tok-type:   #e0af68;
      --tok-str:    #9ece6a;
      --tok-punct:  #7d8799;

      background: var(--paper);
      color: var(--ink);
      font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
      padding: 2.5rem 1.5rem;
      border-radius: 14px;
      box-sizing: border-box;
      max-width: 680px;
      margin: 0 auto;
    }
    .infographic-schema[data-theme="dark"] {
      --ink:        #e8e6e1;
      --ink-soft:   #9a968c;
      --paper:      #121212;
      --paper-alt:  #1e1e26;
      --accent:     #5b8def;
      --accent-soft:#202942;
      --line:       #2c313d;
      --code-bg:    #0e1218;
      --code-ink:   #d7dde8;
    }
    .infographic-schema * { box-sizing: border-box; }

    .schema-eyebrow {
      font-size: 0.72rem; letter-spacing: 0.12em; text-transform: uppercase;
      color: var(--accent); font-weight: 700; margin: 0 0 0.4rem; text-align: center;
    }
    .schema-title { font-size: 1.4rem; font-weight: 700; margin: 0 0 2rem; text-align: center; letter-spacing: -0.01em; }

    /* --- Diagram rows --- */
    .lvl-row {
      display: grid; grid-template-columns: 100px 1fr; align-items: center; gap: 0.75rem;
    }
    .lvl-label { font-size: 0.76rem; color: var(--ink-soft); font-style: italic; text-align: right; }
    .lvl-content { display: flex; gap: 0.5rem; }
    .lvl-content.center { justify-content: center; }
    .lvl-content.spread { justify-content: space-between; }

    .schema-btn {
      background: var(--accent); color: #fff; border: none; border-radius: 8px;
      font: inherit; font-weight: 700; cursor: pointer; transition: transform .15s, box-shadow .15s;
    }
    .schema-btn:hover { transform: translateY(-1px); }
    .schema-btn.is-active { box-shadow: 0 0 0 3px var(--accent-soft), 0 0 0 4.5px var(--accent); }

    .view-btn { flex: 1 1 0; padding: 0.6rem 0.4rem; font-size: 0.78rem; text-align: center; }
    .logical-btn, .physical-btn { width: 100%; max-width: 320px; padding: 0.85rem 1rem; font-size: 0.95rem; text-align: center; }

    /* --- Connectors --- */
    .connector-row { display: grid; grid-template-columns: 100px 1fr; gap: 0.75rem; }
    .connector-row .lvl-label { visibility: hidden; }
    .connector-fan svg { display: block; width: 100%; height: 26px; }
    .connector-line svg { display: block; width: 100%; }
    .connector-line-wrap { display: flex; justify-content: center; }

    /* --- Database --- */
    .db-cylinder svg { display: block; }

    /* --- Detail panel --- */
    .schema-panel {
      margin-top: 2rem; background: var(--paper-alt); border: 1px solid var(--line);
      border-radius: 12px; padding: 1.4rem 1.5rem;
    }
    .schema-panel.is-fading { animation: schemaFade .35s ease; }
    @keyframes schemaFade { from { opacity: 0.2; } to { opacity: 1; } }
    .schema-panel > *:last-child { margin-bottom: 0; }
    .schema-panel-title { font-size: 1.05rem; font-weight: 700; margin: 0 0 0.7rem; color: var(--accent); }
    .schema-panel-list { margin: 0 0 0.9rem; padding-left: 1.1rem; font-size: 0.86rem; line-height: 1.5; }
    .schema-panel-list li { margin-bottom: 0.3rem; }
    .schema-example-label {
      font-size: 0.68rem; text-transform: uppercase; letter-spacing: 0.06em;
      color: var(--ink-soft); font-weight: 700; margin: 0 0 0.3rem;
    }
    .schema-example-text { font-size: 0.85rem; line-height: 1.5; margin: 0 0 0.8rem; }
    .schema-code {
      background: var(--code-bg); color: var(--code-ink);
      border-radius: 8px; padding: 0.8rem 1rem; font-size: 0.78rem; line-height: 1.5;
      overflow-x: auto; margin: 0 0 0.9rem; font-family: "SFMono-Regular", Consolas, "Liberation Mono", Menlo, monospace;
    }
    .tok-kw   { color: var(--tok-kw); font-weight: 600; }
    .tok-type { color: var(--tok-type); }
    .tok-str  { color: var(--tok-str); }
    .tok-punct{ color: var(--tok-punct); }

    .schema-output-label {
      font-size: 0.68rem; text-transform: uppercase; letter-spacing: 0.06em;
      color: var(--ink-soft); font-weight: 700; margin: 0 0 0.4rem;
    }
    .schema-output-table {
      width: 100%; border-collapse: collapse; font-size: 0.82rem;
      background: var(--paper); border: 1px solid var(--line); border-radius: 8px; overflow: hidden;
    }
    .schema-output-table th, .schema-output-table td {
      padding: 0.45rem 0.65rem; text-align: left; border-bottom: 1px solid var(--line);
    }
    .schema-output-table th {
      background: var(--accent-soft); color: var(--accent); font-weight: 700;
      font-size: 0.72rem; text-transform: uppercase; letter-spacing: 0.03em;
    }
    .schema-output-table tr:last-child td { border-bottom: none; }

    @media (max-width: 480px) {
      .lvl-row, .connector-row { grid-template-columns: 60px 1fr; }
      .lvl-label { font-size: 0.65rem; }
      .view-btn { font-size: 0.68rem; padding: 0.5rem 0.25rem; }
    }
    @media (prefers-reduced-motion: reduce) {
      .infographic-schema *, .infographic-schema *::before, .infographic-schema *::after {
        animation-duration: 0.001ms !important; transition-duration: 0.001ms !important;
      }
    }
  </style>

  <p class="schema-eyebrow">Three-Schema Architecture</p>
  <h2 class="schema-title">One Database, Many Views</h2>

  <div class="lvl-row">
    <span class="lvl-label">(View Level)</span>
    <div class="lvl-content spread" id="viewRow"></div>
  </div>

  <div class="connector-row">
    <span class="lvl-label">·</span>
    <div class="connector-fan">
      <svg viewBox="0 0 100 26" preserveAspectRatio="none">
        <path d="M12 0 V13 M37 0 V13 M63 0 V13 M88 0 V13 M12 13 H88 M50 13 V25"
          fill="none" style="stroke:var(--ink-soft)" stroke-width="1.5"/>
      </svg>
    </div>
  </div>

  <div class="lvl-row">
    <span class="lvl-label">(Conceptual Level)</span>
    <div class="lvl-content center" id="logicalRow"></div>
  </div>

  <div class="connector-row">
    <span class="lvl-label">·</span>
    <div class="connector-line-wrap"><span style="color:var(--ink-soft); font-size:1.2rem;">↓</span></div>
  </div>

  <div class="lvl-row">
    <span class="lvl-label">(Internal Level)</span>
    <div class="lvl-content center" id="physicalRow"></div>
  </div>

  <div class="connector-row">
    <span class="lvl-label">·</span>
    <div class="connector-line-wrap"><span style="color:var(--ink-soft); font-size:1.2rem;">↓</span></div>
  </div>

  <div class="lvl-row">
    <span class="lvl-label"></span>
    <div class="lvl-content center db-cylinder" id="dbCylinder"></div>
  </div>

  <div class="schema-panel" id="schemaPanel"></div>
</div>

<script>
(function () {
  var wrapper = document.getElementById('schemaWrap');

  // Dark mode detection — body attribute wins, then cookie, then light default
  var bodyAttr = document.body.getAttribute('data-darkmode');
  var dark;
  if (bodyAttr === 'true') {
    dark = true;
  } else if (bodyAttr === 'false') {
    dark = false;
  } else {
    var match = document.cookie.match(/(?:^|;\s*)darkMode=([^;]+)/);
    dark = match ? match[1] === 'true' : false;
  }
  if (dark) wrapper.setAttribute('data-theme', 'dark');

  // Shared sample data behind every view
  var studentRows = [
    { RollNo: '101', Name: 'Aditi', Class: '10-A', Marks: '88' },
    { RollNo: '102', Name: 'Rohan', Class: '10-A', Marks: '76' }
  ];

  function outputFor(columns) {
    return {
      columns: columns,
      rows: studentRows.map(function (r) { return columns.map(function (c) { return r[c]; }); })
    };
  }

  var views = [
    { label: 'View 1', title: 'View 1 — Teacher View', cols: ['Name', 'Marks'],
      detail: 'A teacher only needs to see names alongside marks — nothing else.' },
    { label: 'View 2', title: 'View 2 — Admin View', cols: ['RollNo', 'Name', 'Class', 'Marks'],
      detail: 'An administrator gets the full record for record-keeping and audits.' },
    { label: 'View 3', title: 'View 3 — Parent View', cols: ['Name', 'Class'],
      detail: 'A parent portal shows the student\u2019s name and class, not marks or IDs.' },
    { label: 'View 4', title: 'View 4 — Office View', cols: ['RollNo', 'Class'],
      detail: 'The front office only needs roll numbers matched to a class for logistics.' }
  ];

  var logicalInfo = {
    title: 'Logical Level (Conceptual)',
    bullets: [
      'Describes what data is stored and the relationships between it.',
      'Defines tables, columns, data types, and constraints.',
      'One conceptual schema feeds every view above it.'
    ],
    example: 'The single Student table that all four views above are built from.',
    code: 'CREATE TABLE Student (\n  RollNo INT,\n  Name VARCHAR(50),\n  Class VARCHAR(10),\n  Marks INT\n);',
    output: outputFor(['RollNo', 'Name', 'Class', 'Marks'])
  };

  var physicalInfo = {
    title: 'Physical Level (Internal)',
    bullets: [
      'Describes how data is actually stored in memory or on disk.',
      'Deals with storage blocks, indexing, and compression.',
      'Completely hidden from end users and view definitions above.'
    ],
    example: 'How the Student table is stored as a file, indexed by roll number, on disk.',
    code: null,
    output: null
  };

  var viewRow = document.getElementById('viewRow');
  var logicalRow = document.getElementById('logicalRow');
  var physicalRow = document.getElementById('physicalRow');
  var dbCylinder = document.getElementById('dbCylinder');
  var panel = document.getElementById('schemaPanel');
  var allButtons = [];

  function clearActive() {
    allButtons.forEach(function (b) { b.classList.remove('is-active'); });
  }

  function highlightSQL(code) {
    var escaped = code.replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/>/g, '&gt;');
    var keywords = /\b(CREATE|VIEW|TABLE|AS|SELECT|FROM|INSERT|INTO|VALUES)\b/g;
    var types = /\b(INT|VARCHAR)\b/g;
    var strings = /('[^']*')/g;
    var punct = /([(),;])/g;
    return escaped
      .replace(keywords, '<span class="tok-kw">$1</span>')
      .replace(types, '<span class="tok-type">$1</span>')
      .replace(strings, '<span class="tok-str">$1</span>')
      .replace(punct, '<span class="tok-punct">$1</span>');
  }

  function buildOutputTable(output) {
    var html = '<p class="schema-output-label">Output</p><table class="schema-output-table"><thead><tr>';
    output.columns.forEach(function (c) { html += '<th>' + c + '</th>'; });
    html += '</tr></thead><tbody>';
    output.rows.forEach(function (row) {
      html += '<tr>';
      row.forEach(function (cell) { html += '<td>' + cell + '</td>'; });
      html += '</tr>';
    });
    html += '</tbody></table>';
    return html;
  }

  function renderViewPanel(v) {
    var out = outputFor(v.cols);
    var html = '<h3 class="schema-panel-title">' + v.title + '</h3>';
    html += '<p class="schema-example-label">What it shows</p>';
    html += '<p class="schema-example-text">' + v.detail + '</p>';
    html += buildOutputTable(out);
    panel.innerHTML = html;
    replay();
  }

  function renderLevelPanel(info) {
    var html = '<h3 class="schema-panel-title">' + info.title + '</h3>';
    html += '<ul class="schema-panel-list">';
    info.bullets.forEach(function (b) { html += '<li>' + b + '</li>'; });
    html += '</ul>';
    html += '<p class="schema-example-label">Example</p>';
    html += '<p class="schema-example-text">' + info.example + '</p>';
    if (info.code) {
      html += '<pre class="schema-code">' + highlightSQL(info.code) + '</pre>';
    }
    if (info.output) {
      html += buildOutputTable(info.output);
    }
    panel.innerHTML = html;
    replay();
  }

  function replay() {
    panel.classList.remove('is-fading');
    void panel.offsetWidth;
    panel.classList.add('is-fading');
  }

  views.forEach(function (v, i) {
    var btn = document.createElement('button');
    btn.type = 'button';
    btn.className = 'schema-btn view-btn' + (i === 0 ? ' is-active' : '');
    btn.textContent = v.label;
    btn.addEventListener('click', function () {
      clearActive();
      btn.classList.add('is-active');
      renderViewPanel(v);
    });
    viewRow.appendChild(btn);
    allButtons.push(btn);
  });

  var logicalBtn = document.createElement('button');
  logicalBtn.type = 'button';
  logicalBtn.className = 'schema-btn logical-btn';
  logicalBtn.textContent = 'Logical Level';
  logicalBtn.addEventListener('click', function () {
    clearActive();
    logicalBtn.classList.add('is-active');
    renderLevelPanel(logicalInfo);
  });
  logicalRow.appendChild(logicalBtn);
  allButtons.push(logicalBtn);

  var physicalBtn = document.createElement('button');
  physicalBtn.type = 'button';
  physicalBtn.className = 'schema-btn physical-btn';
  physicalBtn.textContent = 'Physical Level';
  physicalBtn.addEventListener('click', function () {
    clearActive();
    physicalBtn.classList.add('is-active');
    renderLevelPanel(physicalInfo);
  });
  physicalRow.appendChild(physicalBtn);
  allButtons.push(physicalBtn);

  dbCylinder.innerHTML =
    '<svg width="70" height="60" viewBox="0 0 70 60">' +
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      '<path d="M3 13 C3 19 16 23 35 23 C54 23 67 19 67 13" fill="none" style="stroke:var(--ink-soft)" stroke-width="2"/>' +
    '</svg>' +
    '<div style="text-align:center; font-size:0.75rem; color:var(--ink-soft); margin-top:0.3rem;">Database</div>';

  renderViewPanel(views[0]);
})();
</script>

.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!');
});