mirror of https://github.com/postgres/postgres
Document a bunch of formerly-undocumented date/time operators,
including the SQL-spec OVERLAPS construct.
This commit is contained in:
Tom Lane
parent
05dddf40c2
commit
f176e37975
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@ -1,5 +1,5 @@
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<!--
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$Header: /cvsroot/pgsql/doc/src/sgml/func.sgml,v 1.169 2003/08/31 17:32:18 petere Exp $
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$Header: /cvsroot/pgsql/doc/src/sgml/func.sgml,v 1.170 2003/09/08 19:38:02 tgl Exp $
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PostgreSQL documentation
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-->
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@ -4575,8 +4575,8 @@ substring('foobar' from 'o(.)b') <lineannotation>o</lineannotation>
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<tbody>
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<row>
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<entry> <literal>+</literal> </entry>
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<entry><literal>timestamp '2001-09-28 01:00' + interval '23 hours'</literal></entry>
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<entry><literal>timestamp '2001-09-29 00:00'</literal></entry>
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<entry><literal>date '2001-09-28' + integer '7'</literal></entry>
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<entry><literal>date '2001-10-05'</literal></entry>
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</row>
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<row>
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@ -4585,16 +4585,58 @@ substring('foobar' from 'o(.)b') <lineannotation>o</lineannotation>
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<entry><literal>timestamp '2001-09-28 01:00'</literal></entry>
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</row>
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<row>
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<entry> <literal>+</literal> </entry>
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<entry><literal>date '2001-09-28' + time '03:00'</literal></entry>
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<entry><literal>timestamp '2001-09-28 03:00'</literal></entry>
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</row>
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<row>
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<entry> <literal>+</literal> </entry>
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<entry><literal>time '03:00' + date '2001-09-28'</literal></entry>
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<entry><literal>timestamp '2001-09-28 03:00'</literal></entry>
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</row>
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<row>
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<entry> <literal>+</literal> </entry>
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<entry><literal>interval '1 day' + interval '1 hour'</literal></entry>
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<entry><literal>interval '1 day 01:00'</literal></entry>
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</row>
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<row>
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<entry> <literal>+</literal> </entry>
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<entry><literal>timestamp '2001-09-28 01:00' + interval '23 hours'</literal></entry>
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<entry><literal>timestamp '2001-09-29 00:00'</literal></entry>
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</row>
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<row>
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<entry> <literal>+</literal> </entry>
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<entry><literal>time '01:00' + interval '3 hours'</literal></entry>
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<entry><literal>time '04:00'</literal></entry>
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</row>
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<row>
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<entry> <literal>+</literal> </entry>
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<entry><literal>interval '3 hours' + time '01:00'</literal></entry>
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<entry><literal>time '04:00'</literal></entry>
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</row>
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<row>
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<entry> <literal>-</literal> </entry>
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<entry><literal>timestamp '2001-09-28 23:00' - interval '23 hours'</literal></entry>
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<entry><literal>timestamp '2001-09-28'</literal></entry>
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<entry><literal>- interval '23 hours'</literal></entry>
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<entry><literal>interval '-23:00'</literal></entry>
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</row>
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<row>
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<entry> <literal>-</literal> </entry>
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<entry><literal>date '2001-10-01' - date '2001-09-28'</literal></entry>
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<entry><literal>integer '3'</literal></entry>
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</row>
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<row>
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<entry> <literal>-</literal> </entry>
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<entry><literal>date '2001-10-01' - integer '7'</literal></entry>
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<entry><literal>date '2001-09-24'</literal></entry>
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</row>
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<row>
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@ -4603,28 +4645,58 @@ substring('foobar' from 'o(.)b') <lineannotation>o</lineannotation>
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<entry><literal>timestamp '2001-09-27 23:00'</literal></entry>
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</row>
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<row>
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<entry> <literal>-</literal> </entry>
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<entry><literal>time '05:00' - time '03:00'</literal></entry>
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<entry><literal>interval '02:00'</literal></entry>
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</row>
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<row>
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<entry> <literal>-</literal> </entry>
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<entry><literal>time '05:00' - interval '2 hours'</literal></entry>
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<entry><literal>time '03:00'</literal></entry>
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</row>
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<row>
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<entry> <literal>-</literal> </entry>
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<entry><literal>timestamp '2001-09-28 23:00' - interval '23 hours'</literal></entry>
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<entry><literal>timestamp '2001-09-28 00:00'</literal></entry>
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</row>
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<row>
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<entry> <literal>-</literal> </entry>
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<entry><literal>interval '1 day' - interval '1 hour'</literal></entry>
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<entry><literal>interval '23:00'</literal></entry>
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</row>
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<row>
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<entry> <literal>-</literal> </entry>
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<entry><literal>interval '2 hours' - time '05:00'</literal></entry>
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<entry><literal>time '03:00:00'</literal></entry>
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<entry><literal>time '03:00'</literal></entry>
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</row>
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<row>
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<entry> <literal>-</literal> </entry>
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<entry><literal>timestamp '2001-09-29 03:00' - timestamp '2001-09-27 12:00'</literal></entry>
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<entry><literal>interval '1 day 15:00'</literal></entry>
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</row>
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<row>
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<entry> <literal>*</literal> </entry>
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<entry><literal>interval '1 hour' * int '3'</literal></entry>
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<entry><literal>interval '03:00'</literal></entry>
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<entry><literal>double precision '3.5' * interval '1 hour'</literal></entry>
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<entry><literal>interval '03:30'</literal></entry>
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</row>
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<row>
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<entry> <literal>*</literal> </entry>
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<entry><literal>interval '1 hour' * double precision '3.5'</literal></entry>
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<entry><literal>interval '03:30'</literal></entry>
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</row>
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<row>
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<entry> <literal>/</literal> </entry>
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<entry><literal>interval '1 hour' / int '3'</literal></entry>
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<entry><literal>interval '00:20'</literal></entry>
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<entry><literal>interval '1 hour' / double precision '1.5'</literal></entry>
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<entry><literal>interval '00:40'</literal></entry>
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</row>
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</tbody>
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</tgroup>
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@ -4714,7 +4786,7 @@ substring('foobar' from 'o(.)b') <lineannotation>o</lineannotation>
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linkend="functions-datetime-trunc">
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</entry>
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<entry><literal>date_trunc('hour', timestamp '2001-02-16 20:38:40')</literal></entry>
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<entry><literal>2001-02-16 20:00:00+00</literal></entry>
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<entry><literal>2001-02-16 20:00:00</literal></entry>
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</row>
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<row>
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@ -4788,14 +4860,36 @@ substring('foobar' from 'o(.)b') <lineannotation>o</lineannotation>
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<entry>Current date and time; see <xref
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linkend="functions-datetime-current">
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</entry>
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<entry><literal>timeofday()</literal></entry>
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<entry><literal>Wed Feb 21 17:01:13.000126 2001 EST</literal></entry>
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<entry></entry>
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<entry></entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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<para>
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In addition to these functions, the SQL <literal>OVERLAPS</> keyword is
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supported:
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<synopsis>
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( <replaceable>start1</replaceable>, <replaceable>end1</replaceable> ) OVERLAPS ( <replaceable>start2</replaceable>, <replaceable>end2</replaceable> )
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( <replaceable>start1</replaceable>, <replaceable>length1</replaceable> ) OVERLAPS ( <replaceable>start2</replaceable>, <replaceable>length2</replaceable> )
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</synopsis>
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This expression yields true when two time periods (defined by their
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endpoints) overlap, false when they do not overlap. The endpoints
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can be specified as pairs of dates, times, or timestamps; or as
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a date, time, or timestamp followed by an interval.
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</para>
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<screen>
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SELECT (DATE '2001-02-16', DATE '2001-12-21') OVERLAPS
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(DATE '2001-10-30', DATE '2002-10-30');
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<lineannotation>Result: </lineannotation><computeroutput>true</computeroutput>
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SELECT (DATE '2001-02-16', INTERVAL '100 days') OVERLAPS
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(DATE '2001-10-30', DATE '2002-10-30');
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<lineannotation>Result: </lineannotation><computeroutput>false</computeroutput>
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</screen>
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<sect2 id="functions-datetime-extract">
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<title><function>EXTRACT</function>, <function>date_part</function></title>
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@ -4906,8 +5000,8 @@ SELECT EXTRACT(DOY FROM TIMESTAMP '2001-02-16 20:38:40');
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</para>
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<screen>
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SELECT EXTRACT(EPOCH FROM TIMESTAMP '2001-02-16 20:38:40');
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<lineannotation>Result: </lineannotation><computeroutput>982352320</computeroutput>
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SELECT EXTRACT(EPOCH FROM TIMESTAMP WITH TIME ZONE '2001-02-16 20:38:40-08');
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<lineannotation>Result: </lineannotation><computeroutput>982384720</computeroutput>
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SELECT EXTRACT(EPOCH FROM INTERVAL '5 days 3 hours');
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<lineannotation>Result: </lineannotation><computeroutput>442800</computeroutput>
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@ -5156,11 +5250,14 @@ SELECT date_part('hour', INTERVAL '4 hours 3 minutes');
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date_trunc('<replaceable>field</replaceable>', <replaceable>source</replaceable>)
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</synopsis>
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<replaceable>source</replaceable> is a value expression of type
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<type>timestamp</type>. (Values of type <type>date</type> and
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<type>time</type> are cast automatically.)
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<type>timestamp</type> or <type>interval</>.
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(Values of type <type>date</type> and
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<type>time</type> are cast automatically, to <type>timestamp</type> or
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<type>interval</> respectively.)
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<replaceable>field</replaceable> selects to which precision to
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truncate the time stamp value. The return value is of type
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<type>timestamp</type> with all fields that are less than the
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truncate the input value. The return value is of type
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<type>timestamp</type> or <type>interval</>
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with all fields that are less significant than the
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selected one set to zero (or one, for day and month).
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</para>
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@ -5185,10 +5282,10 @@ date_trunc('<replaceable>field</replaceable>', <replaceable>source</replaceable>
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Examples:
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<screen>
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SELECT date_trunc('hour', TIMESTAMP '2001-02-16 20:38:40');
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<lineannotation>Result: </lineannotation><computeroutput>2001-02-16 20:00:00+00</computeroutput>
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<lineannotation>Result: </lineannotation><computeroutput>2001-02-16 20:00:00</computeroutput>
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SELECT date_trunc('year', TIMESTAMP '2001-02-16 20:38:40');
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<lineannotation>Result: </lineannotation><computeroutput>2001-01-01 00:00:00+00</computeroutput>
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<lineannotation>Result: </lineannotation><computeroutput>2001-01-01 00:00:00</computeroutput>
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</screen>
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</para>
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</sect2>
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