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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 id="docContent" class="container-fluid col-10"><div 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 18.4 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 /></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 <a href="#FUNCTIONS-BITSTRING" class="id_link">#</a></h2></div></div></div><a id="id-1.5.8.12.2" 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>.  (While only
    type <code class="type">bit</code> is mentioned in these tables, values of
    type <code class="type">bit varying</code> can be used interchangeably.)
    Bit strings support the usual comparison operators shown in
    <a class="xref" href="functions-comparison.html#FUNCTIONS-COMPARISON-OP-TABLE" title="Table 9.1. Comparison Operators">Table 9.1</a>, as well as the
    operators shown in <a class="xref" href="functions-bitstring.html#FUNCTIONS-BIT-STRING-OP-TABLE" title="Table 9.14. Bit String Operators">Table 9.14</a>.
   </p><div class="table" id="FUNCTIONS-BIT-STRING-OP-TABLE"><p class="title"><strong>Table 9.14. Bit String Operators</strong></p><div class="table-contents"><table class="table" summary="Bit String Operators" border="1"><colgroup><col /></colgroup><thead><tr><th class="func_table_entry"><p class="func_signature">
        Operator
       </p>
       <p>
        Description
       </p>
       <p>
        Example(s)
       </p></th></tr></thead><tbody><tr><td class="func_table_entry"><p class="func_signature">
        <code class="type">bit</code> <code class="literal">||</code> <code class="type">bit</code>
        → <code class="returnvalue">bit</code>
       </p>
       <p>
        Concatenation
       </p>
       <p>
        <code class="literal">B'10001' || B'011'</code>
        → <code class="returnvalue">10001011</code>
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <code class="type">bit</code> <code class="literal">&amp;</code> <code class="type">bit</code>
        → <code class="returnvalue">bit</code>
       </p>
       <p>
        Bitwise AND (inputs must be of equal length)
       </p>
       <p>
        <code class="literal">B'10001' &amp; B'01101'</code>
        → <code class="returnvalue">00001</code>
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <code class="type">bit</code> <code class="literal">|</code> <code class="type">bit</code>
        → <code class="returnvalue">bit</code>
       </p>
       <p>
        Bitwise OR (inputs must be of equal length)
       </p>
       <p>
        <code class="literal">B'10001' | B'01101'</code>
        → <code class="returnvalue">11101</code>
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <code class="type">bit</code> <code class="literal">#</code> <code class="type">bit</code>
        → <code class="returnvalue">bit</code>
       </p>
       <p>
        Bitwise exclusive OR (inputs must be of equal length)
       </p>
       <p>
        <code class="literal">B'10001' # B'01101'</code>
        → <code class="returnvalue">11100</code>
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <code class="literal">~</code> <code class="type">bit</code>
        → <code class="returnvalue">bit</code>
       </p>
       <p>
        Bitwise NOT
       </p>
       <p>
        <code class="literal">~ B'10001'</code>
        → <code class="returnvalue">01110</code>
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <code class="type">bit</code> <code class="literal">&lt;&lt;</code> <code class="type">integer</code>
        → <code class="returnvalue">bit</code>
       </p>
       <p>
        Bitwise shift left
        (string length is preserved)
       </p>
       <p>
        <code class="literal">B'10001' &lt;&lt; 3</code>
        → <code class="returnvalue">01000</code>
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <code class="type">bit</code> <code class="literal">&gt;&gt;</code> <code class="type">integer</code>
        → <code class="returnvalue">bit</code>
       </p>
       <p>
        Bitwise shift right
        (string length is preserved)
       </p>
       <p>
        <code class="literal">B'10001' &gt;&gt; 2</code>
        → <code class="returnvalue">00100</code>
       </p></td></tr></tbody></table></div></div><br class="table-break" /><p>
    Some of the functions available for binary strings are also available
    for bit strings, as shown in <a class="xref" href="functions-bitstring.html#FUNCTIONS-BIT-STRING-TABLE" title="Table 9.15. Bit String Functions">Table 9.15</a>.
   </p><div class="table" id="FUNCTIONS-BIT-STRING-TABLE"><p class="title"><strong>Table 9.15. Bit String Functions</strong></p><div class="table-contents"><table class="table" summary="Bit String Functions" border="1"><colgroup><col /></colgroup><thead><tr><th class="func_table_entry"><p class="func_signature">
        Function
       </p>
       <p>
        Description
       </p>
       <p>
        Example(s)
       </p></th></tr></thead><tbody><tr><td class="func_table_entry"><p class="func_signature">
        <a id="id-1.5.8.12.6.2.2.1.1.1.1" class="indexterm"></a>
        <code class="function">bit_count</code> ( <code class="type">bit</code> )
        → <code class="returnvalue">bigint</code>
       </p>
       <p>
        Returns the number of bits set in the bit string (also known as
        <span class="quote">“<span class="quote">popcount</span>”</span>).
       </p>
       <p>
        <code class="literal">bit_count(B'10111')</code>
        → <code class="returnvalue">4</code>
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <a id="id-1.5.8.12.6.2.2.2.1.1.1" class="indexterm"></a>
        <code class="function">bit_length</code> ( <code class="type">bit</code> )
        → <code class="returnvalue">integer</code>
       </p>
       <p>
        Returns number of bits in the bit string.
       </p>
       <p>
        <code class="literal">bit_length(B'10111')</code>
        → <code class="returnvalue">5</code>
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <a id="id-1.5.8.12.6.2.2.3.1.1.1" class="indexterm"></a>
        <a id="id-1.5.8.12.6.2.2.3.1.1.2" class="indexterm"></a>
        <code class="function">length</code> ( <code class="type">bit</code> )
        → <code class="returnvalue">integer</code>
       </p>
       <p>
        Returns number of bits in the bit string.
       </p>
       <p>
        <code class="literal">length(B'10111')</code>
        → <code class="returnvalue">5</code>
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <a id="id-1.5.8.12.6.2.2.4.1.1.1" class="indexterm"></a>
        <code class="function">octet_length</code> ( <code class="type">bit</code> )
        → <code class="returnvalue">integer</code>
       </p>
       <p>
        Returns number of bytes in the bit string.
       </p>
       <p>
        <code class="literal">octet_length(B'1011111011')</code>
        → <code class="returnvalue">2</code>
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <a id="id-1.5.8.12.6.2.2.5.1.1.1" class="indexterm"></a>
        <code class="function">overlay</code> ( <em class="parameter"><code>bits</code></em> <code class="type">bit</code> <code class="literal">PLACING</code> <em class="parameter"><code>newsubstring</code></em> <code class="type">bit</code> <code class="literal">FROM</code> <em class="parameter"><code>start</code></em> <code class="type">integer</code> [<span class="optional"> <code class="literal">FOR</code> <em class="parameter"><code>count</code></em> <code class="type">integer</code> </span>] )
        → <code class="returnvalue">bit</code>
       </p>
       <p>
        Replaces the substring of <em class="parameter"><code>bits</code></em> that starts at
        the <em class="parameter"><code>start</code></em>'th bit and extends
        for <em class="parameter"><code>count</code></em> bits
        with <em class="parameter"><code>newsubstring</code></em>.
        If <em class="parameter"><code>count</code></em> is omitted, it defaults to the length
        of <em class="parameter"><code>newsubstring</code></em>.
       </p>
       <p>
        <code class="literal">overlay(B'01010101010101010' placing B'11111' from 2 for 3)</code>
        → <code class="returnvalue">0111110101010101010</code>
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <a id="id-1.5.8.12.6.2.2.6.1.1.1" class="indexterm"></a>
        <code class="function">position</code> ( <em class="parameter"><code>substring</code></em> <code class="type">bit</code> <code class="literal">IN</code> <em class="parameter"><code>bits</code></em> <code class="type">bit</code> )
        → <code class="returnvalue">integer</code>
       </p>
       <p>
        Returns first starting index of the specified <em class="parameter"><code>substring</code></em>
        within <em class="parameter"><code>bits</code></em>, or zero if it's not present.
       </p>
       <p>
        <code class="literal">position(B'010' in B'000001101011')</code>
        → <code class="returnvalue">8</code>
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <a id="id-1.5.8.12.6.2.2.7.1.1.1" class="indexterm"></a>
        <code class="function">substring</code> ( <em class="parameter"><code>bits</code></em> <code class="type">bit</code> [<span class="optional"> <code class="literal">FROM</code> <em class="parameter"><code>start</code></em> <code class="type">integer</code> </span>] [<span class="optional"> <code class="literal">FOR</code> <em class="parameter"><code>count</code></em> <code class="type">integer</code> </span>] )
        → <code class="returnvalue">bit</code>
       </p>
       <p>
        Extracts the substring of <em class="parameter"><code>bits</code></em> starting at
        the <em class="parameter"><code>start</code></em>'th bit if that is specified,
        and stopping after <em class="parameter"><code>count</code></em> bits if that is
        specified.  Provide at least one of <em class="parameter"><code>start</code></em>
        and <em class="parameter"><code>count</code></em>.
       </p>
       <p>
        <code class="literal">substring(B'110010111111' from 3 for 2)</code>
        → <code class="returnvalue">00</code>
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <a id="id-1.5.8.12.6.2.2.8.1.1.1" class="indexterm"></a>
        <code class="function">get_bit</code> ( <em class="parameter"><code>bits</code></em> <code class="type">bit</code>,
        <em class="parameter"><code>n</code></em> <code class="type">integer</code> )
        → <code class="returnvalue">integer</code>
       </p>
       <p>
        Extracts <em class="parameter"><code>n</code></em>'th bit
        from bit string; the first (leftmost) bit is bit 0.
       </p>
       <p>
        <code class="literal">get_bit(B'101010101010101010', 6)</code>
        → <code class="returnvalue">1</code>
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <a id="id-1.5.8.12.6.2.2.9.1.1.1" class="indexterm"></a>
        <code class="function">set_bit</code> ( <em class="parameter"><code>bits</code></em> <code class="type">bit</code>,
        <em class="parameter"><code>n</code></em> <code class="type">integer</code>,
        <em class="parameter"><code>newvalue</code></em> <code class="type">integer</code> )
        → <code class="returnvalue">bit</code>
       </p>
       <p>
        Sets <em class="parameter"><code>n</code></em>'th bit in
        bit string to <em class="parameter"><code>newvalue</code></em>;
        the first (leftmost) bit is bit 0.
       </p>
       <p>
        <code class="literal">set_bit(B'101010101010101010', 6, 0)</code>
        → <code class="returnvalue">101010001010101010</code>
       </p></td></tr></tbody></table></div></div><br class="table-break" /><p>
    In addition, it is possible to cast integral values to and from type
    <code class="type">bit</code>.
    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.
    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><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="functions-binarystring.html" title="9.5. Binary String Functions and Operators">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="functions.html" title="Chapter 9. Functions and Operators">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="functions-matching.html" title="9.7. Pattern Matching">Next</a></td></tr><tr><td width="40%" align="left" valign="top">9.5. Binary String Functions and Operators </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 18.4 Documentation">Home</a></td><td width="40%" align="right" valign="top"> 9.7. Pattern Matching</td></tr></table></div></body></html>