How to Handle NULL in SQL?

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  <h2>Handling NULL in SQL</h2>
  <p class="subtitle">Two things you'll do with NULL constantly: find it, or hide it from the people reading your results. Run both against the same table.</p>

  <div class="tabs" role="tablist">
    <button class="tab is-active" type="button" data-key="check">🔍 Check for NULL</button>
    <button class="tab" type="button" data-key="coalesce">🔄 Replace NULL</button>
  </div>

  <div class="query-box">
    <pre id="sql-text"><span class="kw">SELECT</span> * <span class="kw">FROM</span> Students <span class="kw">WHERE</span> Email <span class="kw">IS NULL</span>;</pre>
  </div>

  <div class="controls">
    <button class="btn" id="btn-run" type="button">▶ Run query</button>
    <button class="btn ghost" id="btn-reset" type="button">↺ Reset</button>
    <span class="run-caption" id="run-caption">Click run to see which rows match.</span>
  </div>

  <table>
    <thead>
      <tr><th>ID</th><th>Name</th><th>Email</th><th>Age</th></tr>
    </thead>
    <tbody id="students-body">
      <tr data-email="set" data-age="set">
        <td>101</td><td>Aisha</td><td>aisha@mail.com</td><td>20</td>
      </tr>
      <tr data-email="null" data-age="set">
        <td>102</td><td>Rahul</td><td><span class="null-tag">NULL</span></td><td>22</td>
      </tr>
      <tr data-email="set" data-age="null">
        <td>103</td><td>Meera</td><td>meera@mail.com</td><td><span class="null-tag">NULL</span></td>
      </tr>
      <tr data-email="null" data-age="set">
        <td>104</td><td>Karan</td><td><span class="null-tag">NULL</span></td><td>19</td>
      </tr>
      <tr data-email="set" data-age="null">
        <td>105</td><td>Priya</td><td>priya@mail.com</td><td><span class="null-tag">NULL</span></td>
      </tr>
    </tbody>
  </table>

  <p class="takeaway"><strong>COALESCE only changes what you see.</strong> The stored Age is still NULL — the query just substitutes a display value for that one result set.</p>

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