">Composite keys</a></h2>

<p>
In relational databases, composite keys depend on two or more fields of a given table.
The analogous concept in Boost.MultiIndex is modeled by means of
<a href="../reference/key_extraction.html#composite_key">
<code>composite_key</code></a>, as shown in the example:
</p>

<blockquote><pre>
<span class=preprocessor>#include</span> <span class=special>&lt;</span><span class=identifier>boost</span><span class=special>/</span><span class=identifier>multi_index_container</span><spa