HTML Code
<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Web SQL — rowsAffected === 0</title>
  <style>
    body {
      font-family: system-ui, sans-serif;
      margin: 0;
      padding: 1.5rem;
      background: #f8fafc;
      color: #334155;
      line-height: 1.6;
    }
    h1 { margin: 0 0 0.5rem; font-size: 1.25rem; color: #0f172a; }
    p { margin: 0 0 1rem; max-width: 460px; }
    button {
      padding: 0.55rem 1rem;
      font-size: 0.9375rem;
      background: #2563eb;
      color: #fff;
      border: none;
      border-radius: 8px;
      cursor: pointer;
    }
    button:hover { background: #1d4ed8; }
    #status {
      margin-top: 1rem;
      padding: 0.75rem 1rem;
      max-width: 460px;
      background: #fff;
      border: 1px solid #e2e8f0;
      border-radius: 8px;
      font-size: 0.875rem;
    }
    #status.ok { border-left: 4px solid #22c55e; }
    #status.warn { border-left: 4px solid #f59e0b; }
    #status.err { border-left: 4px solid #ef4444; }
    code { background: #e2e8f0; padding: 0.1rem 0.35rem; border-radius: 4px; }
  </style>
</head>
<body>
  <h1>Update a missing id</h1>
  <p>User <code>id = 99</code> was never inserted. Click Update and inspect <code>result.rowsAffected</code>.</p>

  <button type="button" id="updateBtn">Update id 99 (Ghost User)</button>

  <p id="status">Click Update id 99 to see rowsAffected === 0.</p>

  <script>
    var statusEl = document.getElementById('status');

    if (!window.openDatabase) {
      statusEl.textContent = 'Web SQL is not supported in this browser.';
      statusEl.className = 'err';
    } else {
      var db = openDatabase('tryitDemo', '1.0', 'Try It DB', 1024 * 1024);

      db.transaction(function (tx) {
        tx.executeSql(
          'CREATE TABLE IF NOT EXISTS users (id INTEGER PRIMARY KEY, name TEXT, age INTEGER)'
        );
      });

      document.getElementById('updateBtn').addEventListener('click', function () {
        var id = 99;
        db.transaction(function (tx) {
          tx.executeSql(
            'UPDATE users SET name = ? WHERE id = ?',
            ['Ghost User', id],
            function (tx, result) {
              if (result.rowsAffected === 0) {
                statusEl.textContent = 'rowsAffected === 0 — no user with id ' + id + '. Not an error, just "not found".';
                statusEl.className = 'warn';
              } else {
                statusEl.textContent = 'Updated ' + result.rowsAffected + ' row(s) for id ' + id;
                statusEl.className = 'ok';
              }
            },
            function (tx, error) {
              statusEl.textContent = 'Error: ' + error.message;
              statusEl.className = 'err';
              return true;
            }
          );
        });
      });
    }
  </script>
</body>
</html>
Lines: 0 | Characters: 0
Live Preview Auto-refresh on Run
Web SQL UPDATE — Detect rowsAffected === 0
