case.html

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            <h1>SQL CASE Statement</h1>

            <p>The CASE statement goes through conditions and returns a value when the first condition is met (like an
                if-then-else statement). Once a condition is true, it will stop reading and return the result. If no
                conditions are true, it returns the value in the ELSE clause.</p>
            <p>If there is no ELSE part and no conditions are true, it returns NULL.</p>

            <h2>CASE Syntax</h2>
            <pre><code class="language-sql">CASE
    WHEN condition1 THEN result1
    WHEN condition2 THEN result2
    WHEN conditionN THEN resultN
    ELSE result
END;</code></pre>

            <h2>SQL CASE Examples</h2>
            <p>The following SQL goes through conditions and returns a value when the first condition is met:</p>
            <pre><code class="language-sql">SELECT patient_id, height,
  CASE
      WHEN height > 175 THEN 'height is greater than 175'
      WHEN height = 175 THEN 'height is 175'
      ELSE 'height is under 175'
  END AS height_group
FROM patients;</code></pre>

            <h2>CASE in ORDER BY Example</h2>
            <p>The following SQL will order the patients by allergies. However, if allergies is NULL, then order by
                patient_id:</p>
            <pre><code class="language-sql">SELECT patient_id, first_name, allergies
FROM patients
ORDER BY
  (CASE
      WHEN allergies IS NULL THEN first_name
      ELSE allergies
  END);</code></pre>
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