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For enum types (described in <a class="xref" href="datatype-enum.html" title="8.7. Enumerated Types">Section 8.7</a>),
there are several functions that allow cleaner programming without
hard-coding particular values of an enum type.
These are listed in <a class="xref" href="functions-enum.html#FUNCTIONS-ENUM-TABLE" title="Table 9.32. Enum Support Functions">Table 9.32</a>. The examples
assume an enum type created as:
</p><pre class="programlisting">
CREATE TYPE rainbow AS ENUM ('red', 'orange', 'yellow', 'green', 'blue', 'purple');
</pre><p>
</p><div class="table" id="FUNCTIONS-ENUM-TABLE"><p class="title"><strong>Table 9.32. Enum Support Functions</strong></p><div class="table-contents"><table class="table" summary="Enum Support Functions" border="1"><colgroup><col /><col /><col /><col /></colgroup><thead><tr><th>Function</th><th>Description</th><th>Example</th><th>Example Result</th></tr></thead><tbody><tr><td>
<a id="id-1.5.8.15.3.2.2.1.1.1" class="indexterm"></a>
<code class="literal">enum_first(anyenum)</code>
</td><td>Returns the first value of the input enum type</td><td><code class="literal">enum_first(null::rainbow)</code></td><td><code class="literal">red</code></td></tr><tr><td>
<a id="id-1.5.8.15.3.2.2.2.1.1" class="indexterm"></a>
<code class="literal">enum_last(anyenum)</code>
</td><td>Returns the last value of the input enum type</td><td><code class="literal">enum_last(null::rainbow)</code></td><td><code class="literal">purple</code></td></tr><tr><td>
<a id="id-1.5.8.15.3.2.2.3.1.1" class="indexterm"></a>
<code class="literal">enum_range(anyenum)</code>
</td><td>Returns all values of the input enum type in an ordered array</td><td><code class="literal">enum_range(null::rainbow)</code></td><td><code class="literal">{red,orange,yellow,green,blue,purple}</code></td></tr><tr><td rowspan="3"><code class="literal">enum_range(anyenum, anyenum)</code></td><td rowspan="3">
Returns the range between the two given enum values, as an ordered
array. The values must be from the same enum type. If the first
parameter is null, the result will start with the first value of
the enum type.
If the second parameter is null, the result will end with the last
value of the enum type.
</td><td><code class="literal">enum_range('orange'::rainbow, 'green'::rainbow)</code></td><td><code class="literal">{orange,yellow,green}</code></td></tr><tr><td><code class="literal">enum_range(NULL, 'green'::rainbow)</code></td><td><code class="literal">{red,orange,yellow,green}</code></td></tr><tr><td><code class="literal">enum_range('orange'::rainbow, NULL)</code></td><td><code class="literal">{orange,yellow,green,blue,purple}</code></td></tr></tbody></table></div></div><br class="table-break" /><p>
Notice that except for the two-argument form of <code class="function">enum_range</code>,
these functions disregard the specific value passed to them; they care
only about its declared data type. Either null or a specific value of
the type can be passed, with the same result. It is more common to
apply these functions to a table column or function argument than to
a hardwired type name as suggested by the examples.
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