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><DIV
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><H1
CLASS="SECT1"
><A
NAME="FUNCTIONS-ARRAY"
>9.18. Array Functions and Operators</A
></H1
><P
> <A
HREF="functions-array.html#ARRAY-OPERATORS-TABLE"
>Table 9-42</A
> shows the operators
available for array types.
</P
><DIV
CLASS="TABLE"
><A
NAME="ARRAY-OPERATORS-TABLE"
></A
><P
><B
>Table 9-42. Array Operators</B
></P
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><COL><COL><COL><COL><THEAD
><TR
><TH
>Operator</TH
><TH
>Description</TH
><TH
>Example</TH
><TH
>Result</TH
></TR
></THEAD
><TBODY
><TR
><TD
> <TT
CLASS="LITERAL"
>=</TT
> </TD
><TD
>equal</TD
><TD
><TT
CLASS="LITERAL"
>ARRAY[1.1,2.1,3.1]::int[] = ARRAY[1,2,3]</TT
></TD
><TD
><TT
CLASS="LITERAL"
>t</TT
></TD
></TR
><TR
><TD
> <TT
CLASS="LITERAL"
><></TT
> </TD
><TD
>not equal</TD
><TD
><TT
CLASS="LITERAL"
>ARRAY[1,2,3] <> ARRAY[1,2,4]</TT
></TD
><TD
><TT
CLASS="LITERAL"
>t</TT
></TD
></TR
><TR
><TD
> <TT
CLASS="LITERAL"
><</TT
> </TD
><TD
>less than</TD
><TD
><TT
CLASS="LITERAL"
>ARRAY[1,2,3] < ARRAY[1,2,4]</TT
></TD
><TD
><TT
CLASS="LITERAL"
>t</TT
></TD
></TR
><TR
><TD
> <TT
CLASS="LITERAL"
>></TT
> </TD
><TD
>greater than</TD
><TD
><TT
CLASS="LITERAL"
>ARRAY[1,4,3] > ARRAY[1,2,4]</TT
></TD
><TD
><TT
CLASS="LITERAL"
>t</TT
></TD
></TR
><TR
><TD
> <TT
CLASS="LITERAL"
><=</TT
> </TD
><TD
>less than or equal</TD
><TD
><TT
CLASS="LITERAL"
>ARRAY[1,2,3] <= ARRAY[1,2,3]</TT
></TD
><TD
><TT
CLASS="LITERAL"
>t</TT
></TD
></TR
><TR
><TD
> <TT
CLASS="LITERAL"
>>=</TT
> </TD
><TD
>greater than or equal</TD
><TD
><TT
CLASS="LITERAL"
>ARRAY[1,4,3] >= ARRAY[1,4,3]</TT
></TD
><TD
><TT
CLASS="LITERAL"
>t</TT
></TD
></TR
><TR
><TD
> <TT
CLASS="LITERAL"
>@></TT
> </TD
><TD
>contains</TD
><TD
><TT
CLASS="LITERAL"
>ARRAY[1,4,3] @> ARRAY[3,1]</TT
></TD
><TD
><TT
CLASS="LITERAL"
>t</TT
></TD
></TR
><TR
><TD
> <TT
CLASS="LITERAL"
><@</TT
> </TD
><TD
>is contained by</TD
><TD
><TT
CLASS="LITERAL"
>ARRAY[2,7] <@ ARRAY[1,7,4,2,6]</TT
></TD
><TD
><TT
CLASS="LITERAL"
>t</TT
></TD
></TR
><TR
><TD
> <TT
CLASS="LITERAL"
>&&</TT
> </TD
><TD
>overlap (have elements in common)</TD
><TD
><TT
CLASS="LITERAL"
>ARRAY[1,4,3] && ARRAY[2,1]</TT
></TD
><TD
><TT
CLASS="LITERAL"
>t</TT
></TD
></TR
><TR
><TD
> <TT
CLASS="LITERAL"
>||</TT
> </TD
><TD
>array-to-array concatenation</TD
><TD
><TT
CLASS="LITERAL"
>ARRAY[1,2,3] || ARRAY[4,5,6]</TT
></TD
><TD
><TT
CLASS="LITERAL"
>{1,2,3,4,5,6}</TT
></TD
></TR
><TR
><TD
> <TT
CLASS="LITERAL"
>||</TT
> </TD
><TD
>array-to-array concatenation</TD
><TD
><TT
CLASS="LITERAL"
>ARRAY[1,2,3] || ARRAY[[4,5,6],[7,8,9]]</TT
></TD
><TD
><TT
CLASS="LITERAL"
>{{1,2,3},{4,5,6},{7,8,9}}</TT
></TD
></TR
><TR
><TD
> <TT
CLASS="LITERAL"
>||</TT
> </TD
><TD
>element-to-array concatenation</TD
><TD
><TT
CLASS="LITERAL"
>3 || ARRAY[4,5,6]</TT
></TD
><TD
><TT
CLASS="LITERAL"
>{3,4,5,6}</TT
></TD
></TR
><TR
><TD
> <TT
CLASS="LITERAL"
>||</TT
> </TD
><TD
>array-to-element concatenation</TD
><TD
><TT
CLASS="LITERAL"
>ARRAY[4,5,6] || 7</TT
></TD
><TD
><TT
CLASS="LITERAL"
>{4,5,6,7}</TT
></TD
></TR
></TBODY
></TABLE
></DIV
><P
> Array comparisons compare the array contents element-by-element,
using the default B-tree comparison function for the element data type.
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
><P
> See <A
HREF="arrays.html"
>Section 8.15</A
> for more details about array operator
behavior.
</P
><P
> <A
HREF="functions-array.html#ARRAY-FUNCTIONS-TABLE"
>Table 9-43</A
> shows the functions
available for use with array types. See <A
HREF="arrays.html"
>Section 8.15</A
>
for more information and examples of the use of these functions.
</P
><DIV
CLASS="TABLE"
><A
NAME="ARRAY-FUNCTIONS-TABLE"
></A
><P
><B
>Table 9-43. Array Functions</B
></P
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><COL><COL><COL><COL><COL><THEAD
><TR
><TH
>Function</TH
><TH
>Return Type</TH
><TH
>Description</TH
><TH
>Example</TH
><TH
>Result</TH
></TR
></THEAD
><TBODY
><TR
><TD
> <TT
CLASS="LITERAL"
> <CODE
CLASS="FUNCTION"
>array_append</CODE
>(<TT
CLASS="TYPE"
>anyarray</TT
>, <TT
CLASS="TYPE"
>anyelement</TT
>)
</TT
>
</TD
><TD
><TT
CLASS="TYPE"
>anyarray</TT
></TD
><TD
>append an element to the end of an array</TD
><TD
><TT
CLASS="LITERAL"
>array_append(ARRAY[1,2], 3)</TT
></TD
><TD
><TT
CLASS="LITERAL"
>{1,2,3}</TT
></TD
></TR
><TR
><TD
> <TT
CLASS="LITERAL"
> <CODE
CLASS="FUNCTION"
>array_cat</CODE
>(<TT
CLASS="TYPE"
>anyarray</TT
>, <TT
CLASS="TYPE"
>anyarray</TT
>)
</TT
>
</TD
><TD
><TT
CLASS="TYPE"
>anyarray</TT
></TD
><TD
>concatenate two arrays</TD
><TD
><TT
CLASS="LITERAL"
>array_cat(ARRAY[1,2,3], ARRAY[4,5])</TT
></TD
><TD
><TT
CLASS="LITERAL"
>{1,2,3,4,5}</TT
></TD
></TR
><TR
><TD
> <TT
CLASS="LITERAL"
> <CODE
CLASS="FUNCTION"
>array_ndims</CODE
>(<TT
CLASS="TYPE"
>anyarray</TT
>)
</TT
>
</TD
><TD
><TT
CLASS="TYPE"
>int</TT
></TD
><TD
>returns the number of dimensions of the array</TD
><TD
><TT
CLASS="LITERAL"
>array_ndims(ARRAY[[1,2,3], [4,5,6]])</TT
></TD
><TD
><TT
CLASS="LITERAL"
>2</TT
></TD
></TR
><TR
><TD
> <TT
CLASS="LITERAL"
> <CODE
CLASS="FUNCTION"
>array_dims</CODE
>(<TT
CLASS="TYPE"
>anyarray</TT
>)
</TT
>
</TD
><TD
><TT
CLASS="TYPE"
>text</TT
></TD
><TD
>returns a text representation of array's dimensions</TD
><TD
><TT
CLASS="LITERAL"
>array_dims(ARRAY[[1,2,3], [4,5,6]])</TT
></TD
><TD
><TT
CLASS="LITERAL"
>[1:2][1:3]</TT
></TD
></TR
><TR
><TD
> <TT
CLASS="LITERAL"
> <CODE
CLASS="FUNCTION"
>array_fill</CODE
>(<TT
CLASS="TYPE"
>anyelement</TT
>, <TT
CLASS="TYPE"
>int[]</TT
>,
[<SPAN
CLASS="OPTIONAL"
>, <TT
CLASS="TYPE"
>int[]</TT
></SPAN
>])
</TT
>
</TD
><TD
><TT
CLASS="TYPE"
>anyarray</TT
></TD
><TD
>returns an array initialized with supplied value and
dimensions, optionally with lower bounds other than 1</TD
><TD
><TT
CLASS="LITERAL"
>array_fill(7, ARRAY[3], ARRAY[2])</TT
></TD
><TD
><TT
CLASS="LITERAL"
>[2:4]={7,7,7}</TT
></TD
></TR
><TR
><TD
> <TT
CLASS="LITERAL"
> <CODE
CLASS="FUNCTION"
>array_length</CODE
>(<TT
CLASS="TYPE"
>anyarray</TT
>, <TT
CLASS="TYPE"
>int</TT
>)
</TT
>
</TD
><TD
><TT
CLASS="TYPE"
>int</TT
></TD
><TD
>returns the length of the requested array dimension</TD
><TD
><TT
CLASS="LITERAL"
>array_length(array[1,2,3], 1)</TT
></TD
><TD
><TT
CLASS="LITERAL"
>3</TT
></TD
></TR
><TR
><TD
> <TT
CLASS="LITERAL"
> <CODE
CLASS="FUNCTION"
>array_lower</CODE
>(<TT
CLASS="TYPE"
>anyarray</TT
>, <TT
CLASS="TYPE"
>int</TT
>)
</TT
>
</TD
><TD
><TT
CLASS="TYPE"
>int</TT
></TD
><TD
>returns lower bound of the requested array dimension</TD
><TD
><TT
CLASS="LITERAL"
>array_lower('[0:2]={1,2,3}'::int[], 1)</TT
></TD
><TD
><TT
CLASS="LITERAL"
>0</TT
></TD
></TR
><TR
><TD
> <TT
CLASS="LITERAL"
> <CODE
CLASS="FUNCTION"
>array_prepend</CODE
>(<TT
CLASS="TYPE"
>anyelement</TT
>, <TT
CLASS="TYPE"
>anyarray</TT
>)
</TT
>
</TD
><TD
><TT
CLASS="TYPE"
>anyarray</TT
></TD
><TD
>append an element to the beginning of an array</TD
><TD
><TT
CLASS="LITERAL"
>array_prepend(1, ARRAY[2,3])</TT
></TD
><TD
><TT
CLASS="LITERAL"
>{1,2,3}</TT
></TD
></TR
><TR
><TD
> <TT
CLASS="LITERAL"
> <CODE
CLASS="FUNCTION"
>array_to_string</CODE
>(<TT
CLASS="TYPE"
>anyarray</TT
>, <TT
CLASS="TYPE"
>text</TT
> [<SPAN
CLASS="OPTIONAL"
>, <TT
CLASS="TYPE"
>text</TT
></SPAN
>])
</TT
>
</TD
><TD
><TT
CLASS="TYPE"
>text</TT
></TD
><TD
>concatenates array elements using supplied delimiter and
optional null string</TD
><TD
><TT
CLASS="LITERAL"
>array_to_string(ARRAY[1, 2, 3, NULL, 5], ',', '*')</TT
></TD
><TD
><TT
CLASS="LITERAL"
>1,2,3,*,5</TT
></TD
></TR
><TR
><TD
> <TT
CLASS="LITERAL"
> <CODE
CLASS="FUNCTION"
>array_upper</CODE
>(<TT
CLASS="TYPE"
>anyarray</TT
>, <TT
CLASS="TYPE"
>int</TT
>)
</TT
>
</TD
><TD
><TT
CLASS="TYPE"
>int</TT
></TD
><TD
>returns upper bound of the requested array dimension</TD
><TD
><TT
CLASS="LITERAL"
>array_upper(ARRAY[1,8,3,7], 1)</TT
></TD
><TD
><TT
CLASS="LITERAL"
>4</TT
></TD
></TR
><TR
><TD
> <TT
CLASS="LITERAL"
> <CODE
CLASS="FUNCTION"
>string_to_array</CODE
>(<TT
CLASS="TYPE"
>text</TT
>, <TT
CLASS="TYPE"
>text</TT
> [<SPAN
CLASS="OPTIONAL"
>, <TT
CLASS="TYPE"
>text</TT
></SPAN
>])
</TT
>
</TD
><TD
><TT
CLASS="TYPE"
>text[]</TT
></TD
><TD
>splits string into array elements using supplied delimiter and
optional null string</TD
><TD
><TT
CLASS="LITERAL"
>string_to_array('xx~^~yy~^~zz', '~^~', 'yy')</TT
></TD
><TD
><TT
CLASS="LITERAL"
>{xx,NULL,zz}</TT
></TD
></TR
><TR
><TD
> <TT
CLASS="LITERAL"
> <CODE
CLASS="FUNCTION"
>unnest</CODE
>(<TT
CLASS="TYPE"
>anyarray</TT
>)
</TT
>
</TD
><TD
><TT
CLASS="TYPE"
>setof anyelement</TT
></TD
><TD
>expand an array to a set of rows</TD
><TD
><TT
CLASS="LITERAL"
>unnest(ARRAY[1,2])</TT
></TD
><TD
><PRE
CLASS="LITERALLAYOUT"
>1
2</PRE
>(2 rows)</TD
></TR
></TBODY
></TABLE
></DIV
><P
> In <CODE
CLASS="FUNCTION"
>string_to_array</CODE
>, if the delimiter parameter is
NULL, each character in the input string will become a separate element in
the resulting array. If the delimiter is an empty string, then the entire
input string is returned as a one-element array. Otherwise the input
string is split at each occurrence of the delimiter string.
</P
><P
> In <CODE
CLASS="FUNCTION"
>string_to_array</CODE
>, if the null-string parameter
is omitted or NULL, none of the substrings of the input will be replaced
by NULL.
In <CODE
CLASS="FUNCTION"
>array_to_string</CODE
>, if the null-string parameter
is omitted or NULL, any null elements in the array are simply skipped
and not represented in the output string.
</P
><DIV
CLASS="NOTE"
><BLOCKQUOTE
CLASS="NOTE"
><P
><B
>Note: </B
> 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 NULL when
the input string is of zero length. Second, if the delimiter string is
NULL, the function splits the input into individual characters, rather
than returning NULL as before.
</P
></BLOCKQUOTE
></DIV
><P
> See also <A
HREF="functions-aggregate.html"
>Section 9.20</A
> about the aggregate
function <CODE
CLASS="FUNCTION"
>array_agg</CODE
> for use with arrays.
</P
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