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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>9.6. Bit String Functions and Operators</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><link rel="prev" href="functions-binarystring.html" title="9.5. Binary String Functions and Operators" /><link rel="next" href="functions-matching.html" title="9.7. Pattern Matching" /></head><body><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">9.6. Bit String Functions and Operators</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="functions-binarystring.html" title="9.5. Binary String Functions and Operators">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="functions.html" title="Chapter 9. Functions and Operators">Up</a></td><th width="60%" align="center">Chapter 9. Functions and Operators</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 11.5 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="functions-matching.html" title="9.7. Pattern Matching">Next</a></td></tr></table><hr></hr></div><div class="sect1" id="FUNCTIONS-BITSTRING"><div class="titlepage"><div><div><h2 class="title" style="clear: both">9.6. Bit String Functions and Operators</h2></div></div></div><a id="id-1.5.8.11.2" class="indexterm"></a><p>
This section describes functions and operators for examining and
manipulating bit strings, that is values of the types
<code class="type">bit</code> and <code class="type">bit varying</code>. Aside from the
usual comparison operators, the operators
shown in <a class="xref" href="functions-bitstring.html#FUNCTIONS-BIT-STRING-OP-TABLE" title="Table 9.13. Bit String Operators">Table 9.13</a> can be used.
Bit string operands of <code class="literal">&</code>, <code class="literal">|</code>,
and <code class="literal">#</code> must be of equal length. When bit
shifting, the original length of the string is preserved, as shown
in the examples.
</p><div class="table" id="FUNCTIONS-BIT-STRING-OP-TABLE"><p class="title"><strong>Table 9.13. Bit String Operators</strong></p><div class="table-contents"><table class="table" summary="Bit String Operators" border="1"><colgroup><col /><col /><col /><col /></colgroup><thead><tr><th>Operator</th><th>Description</th><th>Example</th><th>Result</th></tr></thead><tbody><tr><td> <code class="literal">||</code> </td><td>concatenation</td><td><code class="literal">B'10001' || B'011'</code></td><td><code class="literal">10001011</code></td></tr><tr><td> <code class="literal">&</code> </td><td>bitwise AND</td><td><code class="literal">B'10001' & B'01101'</code></td><td><code class="literal">00001</code></td></tr><tr><td> <code class="literal">|</code> </td><td>bitwise OR</td><td><code class="literal">B'10001' | B'01101'</code></td><td><code class="literal">11101</code></td></tr><tr><td> <code class="literal">#</code> </td><td>bitwise XOR</td><td><code class="literal">B'10001' # B'01101'</code></td><td><code class="literal">11100</code></td></tr><tr><td> <code class="literal">~</code> </td><td>bitwise NOT</td><td><code class="literal">~ B'10001'</code></td><td><code class="literal">01110</code></td></tr><tr><td> <code class="literal"><<</code> </td><td>bitwise shift left</td><td><code class="literal">B'10001' << 3</code></td><td><code class="literal">01000</code></td></tr><tr><td> <code class="literal">>></code> </td><td>bitwise shift right</td><td><code class="literal">B'10001' >> 2</code></td><td><code class="literal">00100</code></td></tr></tbody></table></div></div><br class="table-break" /><p>
The following <acronym class="acronym">SQL</acronym>-standard functions work on bit
strings as well as character strings:
<code class="literal"><code class="function">length</code></code>,
<code class="literal"><code class="function">bit_length</code></code>,
<code class="literal"><code class="function">octet_length</code></code>,
<code class="literal"><code class="function">position</code></code>,
<code class="literal"><code class="function">substring</code></code>,
<code class="literal"><code class="function">overlay</code></code>.
</p><p>
The following functions work on bit strings as well as binary
strings:
<code class="literal"><code class="function">get_bit</code></code>,
<code class="literal"><code class="function">set_bit</code></code>.
When working with a bit string, these functions number the first
(leftmost) bit of the string as bit 0.
</p><p>
In addition, it is possible to cast integral values to and from type
<code class="type">bit</code>.
Some examples:
</p><pre class="programlisting">
44::bit(10) <em class="lineannotation"><span class="lineannotation">0000101100</span></em>
44::bit(3) <em class="lineannotation"><span class="lineannotation">100</span></em>
cast(-44 as bit(12)) <em class="lineannotation"><span class="lineannotation">111111010100</span></em>
'1110'::bit(4)::integer <em class="lineannotation"><span class="lineannotation">14</span></em>
</pre><p>
Note that casting to just <span class="quote">“<span class="quote">bit</span>”</span> means casting to
<code class="literal">bit(1)</code>, and so will deliver only the least significant
bit of the integer.
</p><div class="note"><h3 class="title">Note</h3><p>
Casting an integer to <code class="type">bit(n)</code> copies the rightmost
<code class="literal">n</code> bits. Casting an integer to a bit string width wider
than the integer itself will sign-extend on the left.
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