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<h1 class="title">DESCRIBE FUNCTION</h1>
<h3 id="description">Description</h3>
<p><code>DESCRIBE FUNCTION</code> statement returns the basic metadata information of an
existing function. The metadata information includes the function name, implementing
class and the usage details. If the optional <code>EXTENDED</code> option is specified, the basic
metadata information is returned along with the extended usage information.</p>
<h3 id="syntax">Syntax</h3>
<figure class="highlight"><pre><code class="language-sql" data-lang="sql"><span></span><span class="err">{</span><span class="k">DESC</span> <span class="o">|</span> <span class="k">DESCRIBE</span><span class="err">}</span> <span class="k">FUNCTION</span> <span class="p">[</span><span class="n">EXTENDED</span><span class="p">]</span> <span class="n">function_name</span></code></pre></figure>
<h3 id="parameters">Parameters</h3>
<dl>
<dt><code><em>function_name</em></code></dt>
<dd>
Specifies a name of an existing function in the system. The function name may be
optionally qualified with a database name. If `function_name` is qualified with
a database then the function is resolved from the user specified database, otherwise
it is resolved from the current database.<br /><br />
<b>Syntax:</b>
<code>
[database_name.]function_name
</code>
</dd>
</dl>
<h3 id="examples">Examples</h3>
<figure class="highlight"><pre><code class="language-sql" data-lang="sql"><span></span><span class="c1">-- Describe a builtin scalar function.</span>
<span class="c1">-- Returns function name, implementing class and usage</span>
<span class="k">DESC</span> <span class="k">FUNCTION</span> <span class="k">abs</span><span class="p">;</span>
<span class="o">+</span><span class="c1">-------------------------------------------------------------------+</span>
<span class="o">|</span><span class="n">function_desc</span> <span class="o">|</span>
<span class="o">+</span><span class="c1">-------------------------------------------------------------------+</span>
<span class="o">|</span><span class="k">Function</span><span class="p">:</span> <span class="k">abs</span> <span class="o">|</span>
<span class="o">|</span><span class="k">Class</span><span class="p">:</span> <span class="n">org</span><span class="p">.</span><span class="n">apache</span><span class="p">.</span><span class="n">spark</span><span class="p">.</span><span class="k">sql</span><span class="p">.</span><span class="n">catalyst</span><span class="p">.</span><span class="n">expressions</span><span class="p">.</span><span class="k">Abs</span> <span class="o">|</span>
<span class="o">|</span><span class="k">Usage</span><span class="p">:</span> <span class="k">abs</span><span class="p">(</span><span class="n">expr</span><span class="p">)</span> <span class="o">-</span> <span class="k">Returns</span> <span class="n">the</span> <span class="k">absolute</span> <span class="n">value</span> <span class="k">of</span> <span class="n">the</span> <span class="nb">numeric</span> <span class="n">value</span><span class="p">.</span><span class="o">|</span>
<span class="o">+</span><span class="c1">-------------------------------------------------------------------+</span>
<span class="c1">-- Describe a builtin scalar function.</span>
<span class="c1">-- Returns function name, implementing class and usage and examples.</span>
<span class="k">DESC</span> <span class="k">FUNCTION</span> <span class="n">EXTENDED</span> <span class="k">abs</span><span class="p">;</span>
<span class="o">+</span><span class="c1">-------------------------------------------------------------------+</span>
<span class="o">|</span><span class="n">function_desc</span> <span class="o">|</span>
<span class="o">+</span><span class="c1">-------------------------------------------------------------------+</span>
<span class="o">|</span><span class="k">Function</span><span class="p">:</span> <span class="k">abs</span> <span class="o">|</span>
<span class="o">|</span><span class="k">Class</span><span class="p">:</span> <span class="n">org</span><span class="p">.</span><span class="n">apache</span><span class="p">.</span><span class="n">spark</span><span class="p">.</span><span class="k">sql</span><span class="p">.</span><span class="n">catalyst</span><span class="p">.</span><span class="n">expressions</span><span class="p">.</span><span class="k">Abs</span> <span class="o">|</span>
<span class="o">|</span><span class="k">Usage</span><span class="p">:</span> <span class="k">abs</span><span class="p">(</span><span class="n">expr</span><span class="p">)</span> <span class="o">-</span> <span class="k">Returns</span> <span class="n">the</span> <span class="k">absolute</span> <span class="n">value</span> <span class="k">of</span> <span class="n">the</span> <span class="nb">numeric</span> <span class="n">value</span><span class="p">.</span><span class="o">|</span>
<span class="o">|</span><span class="n">Extended</span> <span class="k">Usage</span><span class="p">:</span> <span class="o">|</span>
<span class="o">|</span> <span class="n">Examples</span><span class="p">:</span> <span class="o">|</span>
<span class="o">|</span> <span class="o">&gt;</span> <span class="k">SELECT</span> <span class="k">abs</span><span class="p">(</span><span class="o">-</span><span class="mi">1</span><span class="p">);</span> <span class="o">|</span>
<span class="o">|</span> <span class="mi">1</span> <span class="o">|</span>
<span class="o">|</span> <span class="o">|</span>
<span class="o">+</span><span class="c1">-------------------------------------------------------------------+</span>
<span class="c1">-- Describe a builtin aggregate function</span>
<span class="k">DESC</span> <span class="k">FUNCTION</span> <span class="k">max</span><span class="p">;</span>
<span class="o">+</span><span class="c1">--------------------------------------------------------------+</span>
<span class="o">|</span><span class="n">function_desc</span> <span class="o">|</span>
<span class="o">+</span><span class="c1">--------------------------------------------------------------+</span>
<span class="o">|</span><span class="k">Function</span><span class="p">:</span> <span class="k">max</span> <span class="o">|</span>
<span class="o">|</span><span class="k">Class</span><span class="p">:</span> <span class="n">org</span><span class="p">.</span><span class="n">apache</span><span class="p">.</span><span class="n">spark</span><span class="p">.</span><span class="k">sql</span><span class="p">.</span><span class="n">catalyst</span><span class="p">.</span><span class="n">expressions</span><span class="p">.</span><span class="k">aggregate</span><span class="p">.</span><span class="k">Max</span><span class="o">|</span>
<span class="o">|</span><span class="k">Usage</span><span class="p">:</span> <span class="k">max</span><span class="p">(</span><span class="n">expr</span><span class="p">)</span> <span class="o">-</span> <span class="k">Returns</span> <span class="n">the</span> <span class="n">maximum</span> <span class="n">value</span> <span class="k">of</span> <span class="o">`</span><span class="n">expr</span><span class="o">`</span><span class="p">.</span> <span class="o">|</span>
<span class="o">+</span><span class="c1">--------------------------------------------------------------+</span>
<span class="c1">-- Describe a builtin user defined aggregate function</span>
<span class="c1">-- Returns function name, implementing class and usage and examples.</span>
<span class="k">DESC</span> <span class="k">FUNCTION</span> <span class="n">EXTENDED</span> <span class="n">explode</span>
<span class="o">+</span><span class="c1">---------------------------------------------------------------+</span>
<span class="o">|</span><span class="n">function_desc</span> <span class="o">|</span>
<span class="o">+</span><span class="c1">---------------------------------------------------------------+</span>
<span class="o">|</span><span class="k">Function</span><span class="p">:</span> <span class="n">explode</span> <span class="o">|</span>
<span class="o">|</span><span class="k">Class</span><span class="p">:</span> <span class="n">org</span><span class="p">.</span><span class="n">apache</span><span class="p">.</span><span class="n">spark</span><span class="p">.</span><span class="k">sql</span><span class="p">.</span><span class="n">catalyst</span><span class="p">.</span><span class="n">expressions</span><span class="p">.</span><span class="n">Explode</span> <span class="o">|</span>
<span class="o">|</span><span class="k">Usage</span><span class="p">:</span> <span class="n">explode</span><span class="p">(</span><span class="n">expr</span><span class="p">)</span> <span class="o">-</span> <span class="n">Separates</span> <span class="n">the</span> <span class="n">elements</span> <span class="k">of</span> <span class="nb">array</span> <span class="o">`</span><span class="n">expr</span><span class="o">`</span> <span class="o">|</span>
<span class="o">|</span> <span class="k">into</span> <span class="n">multiple</span> <span class="k">rows</span><span class="p">,</span> <span class="k">or</span> <span class="n">the</span> <span class="n">elements</span> <span class="k">of</span> <span class="k">map</span> <span class="o">`</span><span class="n">expr</span><span class="o">`</span> <span class="k">into</span> <span class="o">|</span>
<span class="o">|</span> <span class="n">multiple</span> <span class="k">rows</span> <span class="k">and</span> <span class="n">columns</span><span class="p">.</span> <span class="n">Unless</span> <span class="n">specified</span> <span class="n">otherwise</span><span class="p">,</span> <span class="n">uses</span> <span class="o">|</span>
<span class="o">|</span> <span class="n">the</span> <span class="k">default</span> <span class="k">column</span> <span class="n">name</span> <span class="o">`</span><span class="n">col</span><span class="o">`</span> <span class="k">for</span> <span class="n">elements</span> <span class="k">of</span> <span class="n">the</span> <span class="nb">array</span> <span class="k">or</span> <span class="o">|</span>
<span class="o">|</span> <span class="o">`</span><span class="k">key</span><span class="o">`</span> <span class="k">and</span> <span class="o">`</span><span class="n">value</span><span class="o">`</span> <span class="k">for</span> <span class="n">the</span> <span class="n">elements</span> <span class="k">of</span> <span class="n">the</span> <span class="k">map</span><span class="p">.</span> <span class="o">|</span>
<span class="o">|</span><span class="n">Extended</span> <span class="k">Usage</span><span class="p">:</span> <span class="o">|</span>
<span class="o">|</span> <span class="n">Examples</span><span class="p">:</span> <span class="o">|</span>
<span class="o">|</span> <span class="o">&gt;</span> <span class="k">SELECT</span> <span class="n">explode</span><span class="p">(</span><span class="nb">array</span><span class="p">(</span><span class="mi">10</span><span class="p">,</span> <span class="mi">20</span><span class="p">));</span> <span class="o">|</span>
<span class="o">|</span> <span class="mi">10</span> <span class="o">|</span>
<span class="o">|</span> <span class="mi">20</span> <span class="o">|</span>
<span class="o">+</span><span class="c1">---------------------------------------------------------------+</span></code></pre></figure>
<h3 id="related-statements">Related Statements</h3>
<ul>
<li><a href="sql-ref-syntax-aux-describe-database.html">DESCRIBE DATABASE</a></li>
<li><a href="sql-ref-syntax-aux-describe-table.html">DESCRIBE TABLE</a></li>
<li><a href="sql-ref-syntax-aux-describe-query.html">DESCRIBE QUERY</a></li>
</ul>
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