lag.html

<!-- SECCIÓN LAG WINDOW FUNCTION -->
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            <h1>SQL LAG() Window Function</h1>

            <p>The <strong>LAG()</strong> function returns the record offset by the specified amount.</p>

            <h2>Syntax</h2>
            <pre><code class="language-sql">LAG(expression [, offset])</code></pre>

            <h2>Parameter Values</h2>
            <ul>
                <li><strong>expression</strong>: Required. The value to be returned based on the specified offset. Must
                    be a scalar value; cannot be an analytic function.</li>
                <li><strong>offset</strong>: Optional. Number of rows back from the current row. Default is 1. Must be
                    positive; cannot be negative or an analytic function.</li>
            </ul>

            <h2>LAG() Example</h2>
            <p>The following SQL statement displays each patient's <strong>first_name</strong> along with the
                <strong>first_name</strong> of the previous patient:</p>

            <pre><code class="language-sql">SELECT
  patient_id,
  first_name,
  LAG(first_name, 1) OVER() AS previous_name
FROM patients;</code></pre>

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