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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
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<title>8.13. DESCRIBE OUTPUT — Presto 0.186 Documentation</title>
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<div class="header">
<h1 class="heading"><a href="../index.html">
<span>Presto 0.186 Documentation</span></a></h1>
<h2 class="heading"><span>8.13. DESCRIBE OUTPUT</span></h2>
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<div class="content">
<div class="section" id="describe-output">
<h1>8.13. DESCRIBE OUTPUT</h1>
<div class="section" id="synopsis">
<h2>Synopsis</h2>
<div class="highlight-none"><div class="highlight"><pre><span></span>DESCRIBE OUTPUT statement_name
</pre></div>
</div>
</div>
<div class="section" id="description">
<h2>Description</h2>
<p>List the output columns of a prepared statement, including the
column name (or alias), catalog, schema, table, type, type size in
bytes, and a boolean indicating if the column is aliased.</p>
</div>
<div class="section" id="examples">
<h2>Examples</h2>
<p>Prepare and describe a query with four output columns:</p>
<div class="highlight-sql"><div class="highlight"><pre><span></span><span class="k">PREPARE</span> <span class="n">my_select1</span> <span class="k">FROM</span>
<span class="k">SELECT</span> <span class="o">*</span> <span class="k">FROM</span> <span class="n">nation</span>
</pre></div>
</div>
<div class="highlight-sql"><div class="highlight"><pre><span></span><span class="k">DESCRIBE</span> <span class="k">OUTPUT</span> <span class="n">my_select1</span><span class="p">;</span>
</pre></div>
</div>
<div class="highlight-none"><div class="highlight"><pre><span></span> Column Name | Catalog | Schema | Table | Type | Type Size | Aliased
-------------+---------+--------+--------+---------+-----------+---------
nationkey | tpch | sf1 | nation | bigint | 8 | false
name | tpch | sf1 | nation | varchar | 0 | false
regionkey | tpch | sf1 | nation | bigint | 8 | false
comment | tpch | sf1 | nation | varchar | 0 | false
(4 rows)
</pre></div>
</div>
<p>Prepare and describe a query whose output columns are expressions:</p>
<div class="highlight-sql"><div class="highlight"><pre><span></span><span class="k">PREPARE</span> <span class="n">my_select2</span> <span class="k">FROM</span>
<span class="k">SELECT</span> <span class="k">count</span><span class="p">(</span><span class="o">*</span><span class="p">)</span> <span class="k">as</span> <span class="n">my_count</span><span class="p">,</span> <span class="mi">1</span><span class="o">+</span><span class="mi">2</span> <span class="k">FROM</span> <span class="n">nation</span>
</pre></div>
</div>
<div class="highlight-sql"><div class="highlight"><pre><span></span><span class="k">DESCRIBE</span> <span class="k">OUTPUT</span> <span class="n">my_select2</span><span class="p">;</span>
</pre></div>
</div>
<div class="highlight-none"><div class="highlight"><pre><span></span> Column Name | Catalog | Schema | Table | Type | Type Size | Aliased
-------------+---------+--------+-------+--------+-----------+---------
my_count | | | | bigint | 8 | true
_col1 | | | | bigint | 8 | false
(2 rows)
</pre></div>
</div>
<p>Prepare and describe a row count query:</p>
<div class="highlight-sql"><div class="highlight"><pre><span></span><span class="k">PREPARE</span> <span class="n">my_create</span> <span class="k">FROM</span>
<span class="k">CREATE</span> <span class="k">TABLE</span> <span class="n">foo</span> <span class="k">AS</span> <span class="k">SELECT</span> <span class="o">*</span> <span class="k">FROM</span> <span class="n">nation</span>
</pre></div>
</div>
<div class="highlight-sql"><div class="highlight"><pre><span></span><span class="k">DESCRIBE</span> <span class="k">OUTPUT</span> <span class="n">my_create</span><span class="p">;</span>
</pre></div>
</div>
<div class="highlight-none"><div class="highlight"><pre><span></span> Column Name | Catalog | Schema | Table | Type | Type Size | Aliased
-------------+---------+--------+-------+--------+-----------+---------
rows | | | | bigint | 8 | false
(1 row)
</pre></div>
</div>
</div>
<div class="section" id="see-also">
<h2>See Also</h2>
<p><a class="reference internal" href="prepare.html"><span class="doc">PREPARE</span></a></p>
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