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<h1><code>DATEDIFF</code> Function</h1>
  <p>Returns the number of calendar or clock boundaries crossed between two dates. A calendar boundary is a transition
  from one day to the next, from one month to the next, etc. A clock boundary is a transition from one hour of the day
  to the next, one minute of the day to the next, etc.</p>
  <h2>Syntax</h2><code>DATEDIFF(<i>date-part</i>, <i>start-date</i>, <i>end-date</i>)</code><br>
  <h2>Parameters</h2>
  <ul class="args">
    <li>
      <i>date-part</i>: text<br>
      One of the following predefined strings. Each <i>date-part</i> has abbreviated aliases that can be used in place
      of the longer names without affecting the behavior.
      <ul class="enum">
        <li><code>year</code>, <code>yy</code>, <code>yyyy</code></li>
        <li><code>quarter</code>, <code>qq</code>, <code>q</code></li>
        <li><code>month</code>, <code>mm</code>, <code>m</code></li>
        <li><code>dayofyear</code>, <code>dy</code>, <code>y</code></li>
        <li><code>day</code>, <code>dd</code>, <code>d</code></li>
        <li><code>week</code>, <code>wk</code>, <code>ww</code></li>
        <li><code>weekday</code>, <code>dw</code></li>
        <li><code>hour</code>, <code>hh</code></li>
        <li><code>minute</code>, <code>mi</code>, <code>n</code></li>
        <li><code>second</code>, <code>ss</code>, <code>s</code></li>
        <li><code>millisecond</code>, <code>ms</code></li>
      </ul>
    </li>
    <li><i>start-date</i>: text<br>
    A text value that can be parsed into a date/time.<br></li>
    <li><i>end-date</i>: text<br>
    A text value that can be parsed into a date/time.<br></li>
  </ul>
  <h2>Return Value</h2>An integer representing the number of the specified <i>date-part</i> boundaries that are crossed
  between <i>start-date</i> and <i>end-date</i>.<br>
  <h2>Example</h2>
  <pre><i>-- Prints "1" because the clock crosses midnight once.</i><br>PRINT DATEDIFF('day', '2016-03-04 03:53', '2016-03-05 11:53');<br><br><i>-- Prints "1" because the clock crosses the top of the hour once.</i><br>PRINT DATEDIFF('hh', '2016-01-01 03:59', '2016-01-01 04:01');<br><br><i>-- Prints "0" because the clock does not cross the top of the hour.</i><br>PRINT DATEDIFF('hh', '2016-01-01 03:50', '2016-01-01 03:52');<br></pre>
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