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<h1>SQL Functions</h1>
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<p class="intro">SQL has a lot of built-in functions for counting and calculations.</p>
<hr />
<h2>Function Syntax</h2>
<p>The syntax for built-in SQL functions is:</p>
<table class="ex" cellspacing="0" border="1" width="100%">
<tr><td><pre>SELECT function(column) FROM table</pre></td>
</tr></table>
<br />
<hr />
<h2>Types of Functions</h2>
<p>There are several basic types and categories of functions in SQL. The basic types of functions are: </p>
<ul>
<li>Aggregate Functions</li>
<li>Scalar functions</li>
</ul>
<hr />
<h2>Aggregate functions</h2>
<p>Aggregate functions operate against a collection of values, but return a
single value.</p>
<p><b>Note:</b> If used among many other expressions in the item list of a
SELECT statement, the SELECT must have a GROUP BY clause!!</p>
<h3>"Persons" table (used in most examples)</h3>
<table class="ex" cellspacing="0" border="1" width="100%">
<tr>
<th align="left">Name</th>
<th align="left">Age</th>
</tr>
<tr>
<td>Hansen, Ola</td>
<td>34</td>
</tr>
<tr>
<td>Svendson, Tove</td>
<td>45</td>
</tr>
<tr>
<td>Pettersen, Kari</td>
<td>19</td>
</tr>
</table>
<h3>Aggregate functions in MS Access</h3>
<table class="ex" cellspacing="0" border="1" width="100%">
<tr>
<th width="35%" align="left" valign="top">Function</th>
<th width="65%" align="left" valign="top">Description</th>
</tr>
<tr>
<td align="left" valign="top"><a href="func_avg.asp">AVG(column)</a></td>
<td align="left" valign="top">Returns the average value of a column</td>
</tr>
<tr>
<td align="left" valign="top"><a href="func_count.asp">COUNT(column)</a></td>
<td align="left" valign="top">Returns the number of rows (without a NULL
value) of a column</td>
</tr>
<tr>
<td align="left" valign="top"><a href="func_count_ast.asp">COUNT(*)</a></td>
<td align="left" valign="top">Returns the number of selected rows</td>
</tr>
<tr>
<td align="left" valign="top">FIRST(column)</td>
<td align="left" valign="top">Returns the value of the first record in a
specified field</td>
</tr>
<tr>
<td align="left" valign="top">LAST(column)</td>
<td align="left" valign="top">Returns the value of the last record in a
specified field</td>
</tr>
<tr>
<td align="left" valign="top"><a href="func_max.asp">MAX(column)</a></td>
<td align="left" valign="top">Returns the highest value of a column</td>
</tr>
<tr>
<td align="left" valign="top"><a href="func_min.asp">MIN(column)</a></td>
<td align="left" valign="top">Returns the lowest value of a column</td>
</tr>
<tr>
<td align="left" valign="top">STDEV(column)</td>
<td align="left" valign="top"> </td>
</tr>
<tr>
<td align="left" valign="top">STDEVP(column)</td>
<td align="left" valign="top"> </td>
</tr>
<tr>
<td align="left" valign="top"><a href="func_sum.asp">SUM(column)</a></td>
<td align="left" valign="top">Returns the total sum of a column</td>
</tr>
<tr>
<td align="left" valign="top">VAR(column)</td>
<td align="left" valign="top"> </td>
</tr>
<tr>
<td align="left" valign="top">VARP(column)</td>
<td align="left" valign="top"> </td>
</tr>
</table>
<h3>Aggregate functions in SQL Server</h3>
<table class="ex" cellspacing="0" border="1" width="100%">
<tr>
<th width="35%" align="left" valign="top">Function</th>
<th width="65%" align="left" valign="top">Description</th>
</tr>
<tr>
<td align="left" valign="top"><a href="func_avg.asp">AVG(column)</a></td>
<td align="left" valign="top">Returns the average value of a column</td>
</tr>
<tr>
<td align="left" valign="top">BINARY_CHECKSUM</td>
<td align="left" valign="top"> </td>
</tr>
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