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        <span>Presto 0.100 Documentation</span></a></h1>
    <h2 class="heading"><span>5.15. Array Functions and Operators</span></h2>
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  <div class="section" id="array-functions-and-operators">
<h1>5.15. Array Functions and Operators</h1>
<div class="section" id="subscript-operator">
<h2>Subscript Operator: []</h2>
<p>The <tt class="docutils literal"><span class="pre">[]</span></tt> operator is used to access an element of an array and is indexed starting from one:</p>
<div class="highlight-sql"><div class="highlight"><pre><span class="k">SELECT</span> <span class="n">my_array</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span> <span class="k">AS</span> <span class="n">first_element</span>
</pre></div>
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<div class="section" id="concatenation-operator">
<h2>Concatenation Operator: ||</h2>
<p>The <tt class="docutils literal"><span class="pre">||</span></tt> operator is used to concatenate an array with an array or an element of the same type:</p>
<div class="highlight-sql"><div class="highlight"><pre><span class="k">SELECT</span> <span class="nb">ARRAY</span> <span class="p">[</span><span class="mi">1</span><span class="p">]</span> <span class="o">||</span> <span class="nb">ARRAY</span> <span class="p">[</span><span class="mi">2</span><span class="p">];</span> <span class="o">=&gt;</span> <span class="p">[</span><span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">]</span>
<span class="k">SELECT</span> <span class="nb">ARRAY</span> <span class="p">[</span><span class="mi">1</span><span class="p">]</span> <span class="o">||</span> <span class="mi">2</span><span class="p">;</span> <span class="o">=&gt;</span> <span class="p">[</span><span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">]</span>
<span class="k">SELECT</span> <span class="mi">2</span> <span class="o">||</span> <span class="nb">ARRAY</span> <span class="p">[</span><span class="mi">1</span><span class="p">];</span> <span class="o">=&gt;</span> <span class="p">[</span><span class="mi">2</span><span class="p">,</span> <span class="mi">1</span><span class="p">]</span>
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<div class="section" id="array-functions">
<h2>Array Functions</h2>
<dl class="function">
<dt id="array_distinct">
<tt class="descname">array_distinct</tt><big>(</big><em>x</em><big>)</big> &rarr; array</dt>
<dd><p>Remove duplicate values from the array <tt class="docutils literal"><span class="pre">x</span></tt>.</p>
</dd></dl>

<dl class="function">
<dt id="array_sort">
<tt class="descname">array_sort</tt><big>(</big><em>x</em><big>)</big> &rarr; array</dt>
<dd><p>Sorts and returns the array <tt class="docutils literal"><span class="pre">x</span></tt>. The elements of <tt class="docutils literal"><span class="pre">x</span></tt> must be orderable.</p>
</dd></dl>

<dl class="function">
<dt id="cardinality">
<tt class="descname">cardinality</tt><big>(</big><em>x</em><big>)</big> &rarr; bigint</dt>
<dd><p>Returns the cardinality (size) of the array <tt class="docutils literal"><span class="pre">x</span></tt>.</p>
</dd></dl>

<dl class="function">
<dt>
<tt class="descname">concat</tt><big>(</big><em>x</em>, <em>y</em><big>)</big> &rarr; array</dt>
<dd><p>Concatenates the arrays <tt class="docutils literal"><span class="pre">x</span></tt> and <tt class="docutils literal"><span class="pre">y</span></tt>. This function provides the same
functionality as the SQL-standard concatenation operator (<tt class="docutils literal"><span class="pre">||</span></tt>).</p>
</dd></dl>

<dl class="function">
<dt id="contains">
<tt class="descname">contains</tt><big>(</big><em>x</em>, <em>y</em><big>)</big> &rarr; boolean</dt>
<dd><p>Returns true if the array <tt class="docutils literal"><span class="pre">x</span></tt> contains the element <tt class="docutils literal"><span class="pre">y</span></tt>.</p>
</dd></dl>

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