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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>2.2. String Functions and Operators — Presto 0.58 Documentation</title>
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<div class="header">
<h1 class="heading"><a href="../index.html">
<span>Presto 0.58 Documentation</span></a></h1>
<h2 class="heading"><span>2.2. String Functions and Operators</span></h2>
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<div class="content">
<div class="section" id="string-functions-and-operators">
<h1>2.2. String Functions and Operators</h1>
<div class="section" id="string-operators">
<h2>String Operators</h2>
<p>The <tt class="docutils literal"><span class="pre">||</span></tt> operator performs concatenation.</p>
</div>
<div class="section" id="string-functions">
<h2>String Functions</h2>
<div class="admonition warning">
<p class="first admonition-title">Warning</p>
<p class="last">Currently, all of the string functions work incorrectly for Unicode (non-ASCII)
strings. They operate as if strings are a sequence of UTF-8 bytes rather
than a sequence of Unicode characters. For example, <a class="reference internal" href="#length" title="length"><tt class="xref py py-func docutils literal"><span class="pre">length()</span></tt></a> returns
the number of bytes in the UTF-8 representation of the string rather than
the number of unicode characters.</p>
</div>
<dl class="function">
<dt id="char">
<tt class="descname">char</tt><big>(</big><em>n</em><big>)</big> → varchar</dt>
<dd><p>Returns the Unicode code point <tt class="docutils literal"><span class="pre">n</span></tt> as a single character string.</p>
</dd></dl>
<dl class="function">
<dt id="concat">
<tt class="descname">concat</tt><big>(</big><em>string1</em>, <em>string2</em><big>)</big> → varchar</dt>
<dd><p>Returns the concatenation of <tt class="docutils literal"><span class="pre">string1</span></tt> and <tt class="docutils literal"><span class="pre">string2</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="length">
<tt class="descname">length</tt><big>(</big><em>string</em><big>)</big> → bigint</dt>
<dd><p>Returns the length of <tt class="docutils literal"><span class="pre">string</span></tt> in characters.</p>
</dd></dl>
<dl class="function">
<dt id="lower">
<tt class="descname">lower</tt><big>(</big><em>string</em><big>)</big> → varchar</dt>
<dd><p>Converts <tt class="docutils literal"><span class="pre">string</span></tt> to lowercase.</p>
</dd></dl>
<dl class="function">
<dt id="ltrim">
<tt class="descname">ltrim</tt><big>(</big><em>string</em><big>)</big> → varchar</dt>
<dd><p>Removes leading spaces from <tt class="docutils literal"><span class="pre">string</span></tt>.</p>
</dd></dl>
<dl class="function">
<dt id="replace">
<tt class="descname">replace</tt><big>(</big><em>string</em>, <em>search</em><big>)</big> → varchar</dt>
<dd><p>Removes all instances of <tt class="docutils literal"><span class="pre">search</span></tt> from <tt class="docutils literal"><span class="pre">string</span></tt>.</p>
</dd></dl>
<dl class="function">
<dt>
<tt class="descname">replace</tt><big>(</big><em>string</em>, <em>search</em>, <em>replace</em><big>)</big> → varchar</dt>
<dd><p>Replaces all instances of <tt class="docutils literal"><span class="pre">search</span></tt> with <tt class="docutils literal"><span class="pre">replace</span></tt> in <tt class="docutils literal"><span class="pre">string</span></tt>.</p>
</dd></dl>
<dl class="function">
<dt id="reverse">
<tt class="descname">reverse</tt><big>(</big><em>string</em><big>)</big> → varchar</dt>
<dd><p>Returns <tt class="docutils literal"><span class="pre">string</span></tt> with the characters in reverse order.</p>
</dd></dl>
<dl class="function">
<dt id="rtrim">
<tt class="descname">rtrim</tt><big>(</big><em>string</em><big>)</big> → varchar</dt>
<dd><p>Removes trailing spaces from <tt class="docutils literal"><span class="pre">string</span></tt>.</p>
</dd></dl>
<dl class="function">
<dt id="split_part">
<tt class="descname">split_part</tt><big>(</big><em>string</em>, <em>delimiter</em>, <em>index</em><big>)</big> → varchar</dt>
<dd><p>Splits <tt class="docutils literal"><span class="pre">string</span></tt> on <tt class="docutils literal"><span class="pre">delimiter</span></tt> and returns the field <tt class="docutils literal"><span class="pre">index</span></tt>.
Field indexes start with <tt class="docutils literal"><span class="pre">1</span></tt>. If the index is larger than than
the number of fields, then null is returned.</p>
</dd></dl>
<dl class="function">
<dt id="strpos">
<tt class="descname">strpos</tt><big>(</big><em>string</em>, <em>substring</em><big>)</big> → bigint</dt>
<dd><p>Returns the starting position of the first instance of <tt class="docutils literal"><span class="pre">substring</span></tt> in
<tt class="docutils literal"><span class="pre">string</span></tt>. Positions start with <tt class="docutils literal"><span class="pre">1</span></tt>. If not found, <tt class="docutils literal"><span class="pre">0</span></tt> is returned.</p>
</dd></dl>
<dl class="function">
<dt id="substr">
<tt class="descname">substr</tt><big>(</big><em>string</em>, <em>start</em><big>)</big> → varchar</dt>
<dd><p>Returns the rest of <tt class="docutils literal"><span class="pre">string</span></tt> from the starting position <tt class="docutils literal"><span class="pre">start</span></tt>.
Positions start with <tt class="docutils literal"><span class="pre">1</span></tt>. A negative starting position is interpreted
as being relative to the end of the string.</p>
</dd></dl>
<dl class="function">
<dt>
<tt class="descname">substr</tt><big>(</big><em>string</em>, <em>start</em>, <em>length</em><big>)</big> → varchar</dt>
<dd><p>Returns a substring from <tt class="docutils literal"><span class="pre">string</span></tt> of length <tt class="docutils literal"><span class="pre">length</span></tt> from the starting
position <tt class="docutils literal"><span class="pre">start</span></tt>. Positions start with <tt class="docutils literal"><span class="pre">1</span></tt>. A negative starting
position is interpreted as being relative to the end of the string.</p>
</dd></dl>
<dl class="function">
<dt id="trim">
<tt class="descname">trim</tt><big>(</big><em>string</em><big>)</big> → varchar</dt>
<dd><p>Removes leading and trailing spaces from <tt class="docutils literal"><span class="pre">string</span></tt>.</p>
</dd></dl>
<dl class="function">
<dt id="upper">
<tt class="descname">upper</tt><big>(</big><em>string</em><big>)</big> → varchar</dt>
<dd><p>Converts <tt class="docutils literal"><span class="pre">string</span></tt> to uppercase.</p>
</dd></dl>
</div>
</div>
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