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<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!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>9.19. Array 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 V1.79.1" /><link rel="prev" href="functions-conditional.html" title="9.18. Conditional Expressions" /><link rel="next" href="functions-range.html" title="9.20. Range Functions and Operators" /></head><body id="docContent" class="container-fluid col-10"><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">9.19. Array Functions and Operators</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="functions-conditional.html" title="9.18. Conditional Expressions">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 13.4 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="functions-range.html" title="9.20. Range Functions and Operators">Next</a></td></tr></table><hr></hr></div><div class="sect1" id="FUNCTIONS-ARRAY"><div class="titlepage"><div><div><h2 class="title" style="clear: both">9.19. Array Functions and Operators</h2></div></div></div><p>
<a class="xref" href="functions-array.html#ARRAY-OPERATORS-TABLE" title="Table 9.51. Array Operators">Table 9.51</a> shows the specialized operators
available for array types.
In addition to those, 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> are available for
arrays. The comparison operators compare the array contents
element-by-element, using the default B-tree comparison function for
the element data type, and sort based on the first difference.
In multidimensional arrays the elements are visited in row-major order
(last subscript varies most rapidly).
If the contents of two arrays are equal but the dimensionality is
different, the first difference in the dimensionality information
determines the sort order. (This is a change from versions of
<span class="productname">PostgreSQL</span> prior to 8.2: older versions would claim
that two arrays with the same contents were equal, even if the
number of dimensions or subscript ranges were different.)
</p><div class="table" id="ARRAY-OPERATORS-TABLE"><p class="title"><strong>Table 9.51. Array Operators</strong></p><div class="table-contents"><table class="table" summary="Array 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">anyarray</code> <code class="literal">@></code> <code class="type">anyarray</code>
→ <code class="returnvalue">boolean</code>
</p>
<p>
Does the first array contain the second, that is, does each element
appearing in the second array equal some element of the first array?
(Duplicates are not treated specially,
thus <code class="literal">ARRAY[1]</code> and <code class="literal">ARRAY[1,1]</code> are
each considered to contain the other.)
</p>
<p>
<code class="literal">ARRAY[1,4,3] @> ARRAY[3,1,3]</code>
→ <code class="returnvalue">t</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="type">anyarray</code> <code class="literal"><@</code> <code class="type">anyarray</code>
→ <code class="returnvalue">boolean</code>
</p>
<p>
Is the first array contained by the second?
</p>
<p>
<code class="literal">ARRAY[2,2,7] <@ ARRAY[1,7,4,2,6]</code>
→ <code class="returnvalue">t</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="type">anyarray</code> <code class="literal">&&</code> <code class="type">anyarray</code>
→ <code class="returnvalue">boolean</code>
</p>
<p>
Do the arrays overlap, that is, have any elements in common?
</p>
<p>
<code class="literal">ARRAY[1,4,3] && ARRAY[2,1]</code>
→ <code class="returnvalue">t</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="type">anyarray</code> <code class="literal">||</code> <code class="type">anyarray</code>
→ <code class="returnvalue">anyarray</code>
</p>
<p>
Concatenates the two arrays. Concatenating a null or empty array is a
no-op; otherwise the arrays must have the same number of dimensions
(as illustrated by the first example) or differ in number of
dimensions by one (as illustrated by the second).
</p>
<p>
<code class="literal">ARRAY[1,2,3] || ARRAY[4,5,6,7]</code>
→ <code class="returnvalue">{1,2,3,4,5,6,7}</code>
</p>
<p>
<code class="literal">ARRAY[1,2,3] || ARRAY[[4,5,6],[7,8,9]]</code>
→ <code class="returnvalue">{{1,2,3},{4,5,6},{7,8,9}}</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="type">anyelement</code> <code class="literal">||</code> <code class="type">anyarray</code>
→ <code class="returnvalue">anyarray</code>
</p>
<p>
Concatenates an element onto the front of an array (which must be
empty or one-dimensional).
</p>
<p>
<code class="literal">3 || ARRAY[4,5,6]</code>
→ <code class="returnvalue">{3,4,5,6}</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="type">anyarray</code> <code class="literal">||</code> <code class="type">anyelement</code>
→ <code class="returnvalue">anyarray</code>
</p>
<p>
Concatenates an element onto the end of an array (which must be
empty or one-dimensional).
</p>
<p>
<code class="literal">ARRAY[4,5,6] || 7</code>
→ <code class="returnvalue">{4,5,6,7}</code>
</p></td></tr></tbody></table></div></div><br class="table-break" /><p>
See <a class="xref" href="arrays.html" title="8.15. Arrays">Section 8.15</a> for more details about array operator
behavior. See <a class="xref" href="indexes-types.html" title="11.2. Index Types">Section 11.2</a> for more details about
which operators support indexed operations.
</p><p>
<a class="xref" href="functions-array.html#ARRAY-FUNCTIONS-TABLE" title="Table 9.52. Array Functions">Table 9.52</a> shows the functions
available for use with array types. See <a class="xref" href="arrays.html" title="8.15. Arrays">Section 8.15</a>
for more information and examples of the use of these functions.
</p><div class="table" id="ARRAY-FUNCTIONS-TABLE"><p class="title"><strong>Table 9.52. Array Functions</strong></p><div class="table-contents"><table class="table" summary="Array 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-1.5.8.25.6.2.2.1.1.1.1" class="indexterm"></a>
<code class="function">array_append</code> ( <code class="type">anyarray</code>, <code class="type">anyelement</code> )
→ <code class="returnvalue">anyarray</code>
</p>
<p>
Appends an element to the end of an array (same as
the <code class="type">anyarray</code> <code class="literal">||</code> <code class="type">anyelement</code>
operator).
</p>
<p>
<code class="literal">array_append(ARRAY[1,2], 3)</code>
→ <code class="returnvalue">{1,2,3}</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<a id="id-1.5.8.25.6.2.2.2.1.1.1" class="indexterm"></a>
<code class="function">array_cat</code> ( <code class="type">anyarray</code>, <code class="type">anyarray</code> )
→ <code class="returnvalue">anyarray</code>
</p>
<p>
Concatenates two arrays (same as
the <code class="type">anyarray</code> <code class="literal">||</code> <code class="type">anyarray</code>
operator).
</p>
<p>
<code class="literal">array_cat(ARRAY[1,2,3], ARRAY[4,5])</code>
→ <code class="returnvalue">{1,2,3,4,5}</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<a id="id-1.5.8.25.6.2.2.3.1.1.1" class="indexterm"></a>
<code class="function">array_dims</code> ( <code class="type">anyarray</code> )
→ <code class="returnvalue">text</code>
</p>
<p>
Returns a text representation of the array's dimensions.
</p>
<p>
<code class="literal">array_dims(ARRAY[[1,2,3], [4,5,6]])</code>
→ <code class="returnvalue">[1:2][1:3]</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<a id="id-1.5.8.25.6.2.2.4.1.1.1" class="indexterm"></a>
<code class="function">array_fill</code> ( <code class="type">anyelement</code>, <code class="type">integer[]</code>
[<span class="optional">, <code class="type">integer[]</code> </span>] )
→ <code class="returnvalue">anyarray</code>
</p>
<p>
Returns an array filled with copies of the given value, having
dimensions of the lengths specified by the second argument.
The optional third argument supplies lower-bound values for each
dimension (which default to all <code class="literal">1</code>).
</p>
<p>
<code class="literal">array_fill(11, ARRAY[2,3])</code>
→ <code class="returnvalue">{{11,11,11},{11,11,11}}</code>
</p>
<p>
<code class="literal">array_fill(7, ARRAY[3], ARRAY[2])</code>
→ <code class="returnvalue">[2:4]={7,7,7}</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<a id="id-1.5.8.25.6.2.2.5.1.1.1" class="indexterm"></a>
<code class="function">array_length</code> ( <code class="type">anyarray</code>, <code class="type">integer</code> )
→ <code class="returnvalue">integer</code>
</p>
<p>
Returns the length of the requested array dimension.
</p>
<p>
<code class="literal">array_length(array[1,2,3], 1)</code>
→ <code class="returnvalue">3</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<a id="id-1.5.8.25.6.2.2.6.1.1.1" class="indexterm"></a>
<code class="function">array_lower</code> ( <code class="type">anyarray</code>, <code class="type">integer</code> )
→ <code class="returnvalue">integer</code>
</p>
<p>
Returns the lower bound of the requested array dimension.
</p>
<p>
<code class="literal">array_lower('[0:2]={1,2,3}'::integer[], 1)</code>
→ <code class="returnvalue">0</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<a id="id-1.5.8.25.6.2.2.7.1.1.1" class="indexterm"></a>
<code class="function">array_ndims</code> ( <code class="type">anyarray</code> )
→ <code class="returnvalue">integer</code>
</p>
<p>
Returns the number of dimensions of the array.
</p>
<p>
<code class="literal">array_ndims(ARRAY[[1,2,3], [4,5,6]])</code>
→ <code class="returnvalue">2</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<a id="id-1.5.8.25.6.2.2.8.1.1.1" class="indexterm"></a>
<code class="function">array_position</code> ( <code class="type">anyarray</code>, <code class="type">anyelement</code> [<span class="optional">, <code class="type">integer</code> </span>] )
→ <code class="returnvalue">integer</code>
</p>
<p>
Returns the subscript of the first occurrence of the second argument
in the array, or <code class="literal">NULL</code> if it's not present.
If the third argument is given, the search begins at that subscript.
The array must be one-dimensional.
Comparisons are done using <code class="literal">IS NOT DISTINCT FROM</code>
semantics, so it is possible to search for <code class="literal">NULL</code>.
</p>
<p>
<code class="literal">array_position(ARRAY['sun', 'mon', 'tue', 'wed', 'thu', 'fri', 'sat'], 'mon')</code>
→ <code class="returnvalue">2</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<a id="id-1.5.8.25.6.2.2.9.1.1.1" class="indexterm"></a>
<code class="function">array_positions</code> ( <code class="type">anyarray</code>, <code class="type">anyelement</code> )
→ <code class="returnvalue">integer[]</code>
</p>
<p>
Returns an array of the subscripts of all occurrences of the second
argument in the array given as first argument.
The array must be one-dimensional.
Comparisons are done using <code class="literal">IS NOT DISTINCT FROM</code>
semantics, so it is possible to search for <code class="literal">NULL</code>.
<code class="literal">NULL</code> is returned only if the array
is <code class="literal">NULL</code>; if the value is not found in the array, an
empty array is returned.
</p>
<p>
<code class="literal">array_positions(ARRAY['A','A','B','A'], 'A')</code>
→ <code class="returnvalue">{1,2,4}</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<a id="id-1.5.8.25.6.2.2.10.1.1.1" class="indexterm"></a>
<code class="function">array_prepend</code> ( <code class="type">anyelement</code>, <code class="type">anyarray</code> )
→ <code class="returnvalue">anyarray</code>
</p>
<p>
Prepends an element to the beginning of an array (same as
the <code class="type">anyelement</code> <code class="literal">||</code> <code class="type">anyarray</code>
operator).
</p>
<p>
<code class="literal">array_prepend(1, ARRAY[2,3])</code>
→ <code class="returnvalue">{1,2,3}</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<a id="id-1.5.8.25.6.2.2.11.1.1.1" class="indexterm"></a>
<code class="function">array_remove</code> ( <code class="type">anyarray</code>, <code class="type">anyelement</code> )
→ <code class="returnvalue">anyarray</code>
</p>
<p>
Removes all elements equal to the given value from the array.
The array must be one-dimensional.
Comparisons are done using <code class="literal">IS NOT DISTINCT FROM</code>
semantics, so it is possible to remove <code class="literal">NULL</code>s.
</p>
<p>
<code class="literal">array_remove(ARRAY[1,2,3,2], 2)</code>
→ <code class="returnvalue">{1,3}</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<a id="id-1.5.8.25.6.2.2.12.1.1.1" class="indexterm"></a>
<code class="function">array_replace</code> ( <code class="type">anyarray</code>, <code class="type">anyelement</code>, <code class="type">anyelement</code> )
→ <code class="returnvalue">anyarray</code>
</p>
<p>
Replaces each array element equal to the second argument with the
third argument.
</p>
<p>
<code class="literal">array_replace(ARRAY[1,2,5,4], 5, 3)</code>
→ <code class="returnvalue">{1,2,3,4}</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<a id="id-1.5.8.25.6.2.2.13.1.1.1" class="indexterm"></a>
<code class="function">array_to_string</code> ( <em class="parameter"><code>array</code></em> <code class="type">anyarray</code>, <em class="parameter"><code>delimiter</code></em> <code class="type">text</code> [<span class="optional">, <em class="parameter"><code>null_string</code></em> <code class="type">text</code> </span>] )
→ <code class="returnvalue">text</code>
</p>
<p>
Converts each array element to its text representation, and
concatenates those separated by
the <em class="parameter"><code>delimiter</code></em> string.
If <em class="parameter"><code>null_string</code></em> is given and is
not <code class="literal">NULL</code>, then <code class="literal">NULL</code> array
entries are represented by that string; otherwise, they are omitted.
</p>
<p>
<code class="literal">array_to_string(ARRAY[1, 2, 3, NULL, 5], ',', '*')</code>
→ <code class="returnvalue">1,2,3,*,5</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<a id="id-1.5.8.25.6.2.2.14.1.1.1" class="indexterm"></a>
<code class="function">array_upper</code> ( <code class="type">anyarray</code>, <code class="type">integer</code> )
→ <code class="returnvalue">integer</code>
</p>
<p>
Returns the upper bound of the requested array dimension.
</p>
<p>
<code class="literal">array_upper(ARRAY[1,8,3,7], 1)</code>
→ <code class="returnvalue">4</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<a id="id-1.5.8.25.6.2.2.15.1.1.1" class="indexterm"></a>
<code class="function">cardinality</code> ( <code class="type">anyarray</code> )
→ <code class="returnvalue">integer</code>
</p>
<p>
Returns the total number of elements in the array, or 0 if the array
is empty.
</p>
<p>
<code class="literal">cardinality(ARRAY[[1,2],[3,4]])</code>
→ <code class="returnvalue">4</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<a id="id-1.5.8.25.6.2.2.16.1.1.1" class="indexterm"></a>
<code class="function">string_to_array</code> ( <em class="parameter"><code>string</code></em> <code class="type">text</code>, <em class="parameter"><code>delimiter</code></em> <code class="type">text</code> [<span class="optional">, <em class="parameter"><code>null_string</code></em> <code class="type">text</code> </span>] )
→ <code class="returnvalue">text[]</code>
</p>
<p>
Splits the <em class="parameter"><code>string</code></em> at occurrences
of <em class="parameter"><code>delimiter</code></em> and forms the remaining data
into a <code class="type">text</code> array.
If <em class="parameter"><code>delimiter</code></em> is <code class="literal">NULL</code>,
each character in the <em class="parameter"><code>string</code></em> will become a
separate element in the array.
If <em class="parameter"><code>delimiter</code></em> is an empty string, then
the <em class="parameter"><code>string</code></em> is treated as a single field.
If <em class="parameter"><code>null_string</code></em> is supplied and is
not <code class="literal">NULL</code>, fields matching that string are converted
to <code class="literal">NULL</code> entries.
</p>
<p>
<code class="literal">string_to_array('xx~~yy~~zz', '~~', 'yy')</code>
→ <code class="returnvalue">{xx,NULL,zz}</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<a id="id-1.5.8.25.6.2.2.17.1.1.1" class="indexterm"></a>
<code class="function">unnest</code> ( <code class="type">anyarray</code> )
→ <code class="returnvalue">setof anyelement</code>
</p>
<p>
Expands an array into a set of rows.
The array's elements are read out in storage order.
</p>
<p>
<code class="literal">unnest(ARRAY[1,2])</code>
→ <code class="returnvalue"></code>
</p><pre class="programlisting">
1
2
</pre><p>
</p>
<p>
<code class="literal">unnest(ARRAY[['foo','bar'],['baz','quux']])</code>
→ <code class="returnvalue"></code>
</p><pre class="programlisting">
foo
bar
baz
quux
</pre><p>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="function">unnest</code> ( <code class="type">anyarray</code>, <code class="type">anyarray</code> [<span class="optional">, ... </span>] )
→ <code class="returnvalue">setof anyelement, anyelement [, ... ]</code>
</p>
<p>
Expands multiple arrays (possibly of different data types) into a set of
rows. If the arrays are not all the same length then the shorter ones
are padded with <code class="literal">NULL</code>s. This form is only allowed
in a query's FROM clause; see <a class="xref" href="queries-table-expressions.html#QUERIES-TABLEFUNCTIONS" title="7.2.1.4. Table Functions">Section 7.2.1.4</a>.
</p>
<p>
<code class="literal">select * from unnest(ARRAY[1,2], ARRAY['foo','bar','baz']) as x(a,b)</code>
→ <code class="returnvalue"></code>
</p><pre class="programlisting">
a | b
---+-----
1 | foo
2 | bar
| baz
</pre><p>
</p></td></tr></tbody></table></div></div><br class="table-break" /><div class="note"><h3 class="title">Note</h3><p>
There are two differences in the behavior of <code class="function">string_to_array</code>
from pre-9.1 versions of <span class="productname">PostgreSQL</span>.
First, it will return an empty (zero-element) array rather
than <code class="literal">NULL</code> when the input string is of zero length.
Second, if the delimiter string is <code class="literal">NULL</code>, the function
splits the input into individual characters, rather than
returning <code class="literal">NULL</code> as before.
</p></div><p>
See also <a class="xref" href="functions-aggregate.html" title="9.21. Aggregate Functions">Section 9.21</a> about the aggregate
function <code class="function">array_agg</code> for use with arrays.
</p></div><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navfooter"><hr></hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="functions-conditional.html" title="9.18. Conditional Expressions">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-range.html" title="9.20. Range Functions and Operators">Next</a></td></tr><tr><td width="40%" align="left" valign="top">9.18. Conditional Expressions </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 13.4 Documentation">Home</a></td><td width="40%" align="right" valign="top"> 9.20. Range Functions and Operators</td></tr></table></div></body></html>
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