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Document a bunch of formerly-undocumented date/time operators,

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including the SQL-spec OVERLAPS construct.
REL7_4_STABLE
Tom Lane 22 years ago
parent 05dddf40c2
commit f176e37975
1 changed files with 118 additions and 21 deletions
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  1. 139
      doc/src/sgml/func.sgml

139
doc/src/sgml/func.sgml
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@ -1,5 +1,5 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/func.sgml,v 1.169 2003/08/31 17:32:18 petere Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/func.sgml,v 1.170 2003/09/08 19:38:02 tgl Exp $
PostgreSQL documentation
-->
@ -4575,8 +4575,8 @@ substring('foobar' from 'o(.)b') <lineannotation>o</lineannotation>
<tbody>
<row>
<entry> <literal>+</literal> </entry>
<entry><literal>timestamp '2001-09-28 01:00' + interval '23 hours'</literal></entry>
<entry><literal>timestamp '2001-09-29 00:00'</literal></entry>
<entry><literal>date '2001-09-28' + integer '7'</literal></entry>
<entry><literal>date '2001-10-05'</literal></entry>
</row>
<row>
@ -4585,16 +4585,58 @@ substring('foobar' from 'o(.)b') <lineannotation>o</lineannotation>
<entry><literal>timestamp '2001-09-28 01:00'</literal></entry>
</row>
<row>
<entry> <literal>+</literal> </entry>
<entry><literal>date '2001-09-28' + time '03:00'</literal></entry>
<entry><literal>timestamp '2001-09-28 03:00'</literal></entry>
</row>
<row>
<entry> <literal>+</literal> </entry>
<entry><literal>time '03:00' + date '2001-09-28'</literal></entry>
<entry><literal>timestamp '2001-09-28 03:00'</literal></entry>
</row>
<row>
<entry> <literal>+</literal> </entry>
<entry><literal>interval '1 day' + interval '1 hour'</literal></entry>
<entry><literal>interval '1 day 01:00'</literal></entry>
</row>
<row>
<entry> <literal>+</literal> </entry>
<entry><literal>timestamp '2001-09-28 01:00' + interval '23 hours'</literal></entry>
<entry><literal>timestamp '2001-09-29 00:00'</literal></entry>
</row>
<row>
<entry> <literal>+</literal> </entry>
<entry><literal>time '01:00' + interval '3 hours'</literal></entry>
<entry><literal>time '04:00'</literal></entry>
</row>
<row>
<entry> <literal>+</literal> </entry>
<entry><literal>interval '3 hours' + time '01:00'</literal></entry>
<entry><literal>time '04:00'</literal></entry>
</row>
<row>
<entry> <literal>-</literal> </entry>
<entry><literal>timestamp '2001-09-28 23:00' - interval '23 hours'</literal></entry>
<entry><literal>timestamp '2001-09-28'</literal></entry>
<entry><literal>- interval '23 hours'</literal></entry>
<entry><literal>interval '-23:00'</literal></entry>
</row>
<row>
<entry> <literal>-</literal> </entry>
<entry><literal>date '2001-10-01' - date '2001-09-28'</literal></entry>
<entry><literal>integer '3'</literal></entry>
</row>
<row>
<entry> <literal>-</literal> </entry>
<entry><literal>date '2001-10-01' - integer '7'</literal></entry>
<entry><literal>date '2001-09-24'</literal></entry>
</row>
<row>
@ -4603,28 +4645,58 @@ substring('foobar' from 'o(.)b') <lineannotation>o</lineannotation>
<entry><literal>timestamp '2001-09-27 23:00'</literal></entry>
</row>
<row>
<entry> <literal>-</literal> </entry>
<entry><literal>time '05:00' - time '03:00'</literal></entry>
<entry><literal>interval '02:00'</literal></entry>
</row>
<row>
<entry> <literal>-</literal> </entry>
<entry><literal>time '05:00' - interval '2 hours'</literal></entry>
<entry><literal>time '03:00'</literal></entry>
</row>
<row>
<entry> <literal>-</literal> </entry>
<entry><literal>timestamp '2001-09-28 23:00' - interval '23 hours'</literal></entry>
<entry><literal>timestamp '2001-09-28 00:00'</literal></entry>
</row>
<row>
<entry> <literal>-</literal> </entry>
<entry><literal>interval '1 day' - interval '1 hour'</literal></entry>
<entry><literal>interval '23:00'</literal></entry>
</row>
<row>
<entry> <literal>-</literal> </entry>
<entry><literal>interval '2 hours' - time '05:00'</literal></entry>
<entry><literal>time '03:00:00'</literal></entry>
<entry><literal>time '03:00'</literal></entry>
</row>
<row>
<entry> <literal>-</literal> </entry>
<entry><literal>timestamp '2001-09-29 03:00' - timestamp '2001-09-27 12:00'</literal></entry>
<entry><literal>interval '1 day 15:00'</literal></entry>
</row>
<row>
<entry> <literal>*</literal> </entry>
<entry><literal>double precision '3.5' * interval '1 hour'</literal></entry>
<entry><literal>interval '03:30'</literal></entry>
</row>
<row>
<entry> <literal>*</literal> </entry>
<entry><literal>interval '1 hour' * int '3'</literal></entry>
<entry><literal>interval '03:00'</literal></entry>
<entry><literal>interval '1 hour' * double precision '3.5'</literal></entry>
<entry><literal>interval '03:30'</literal></entry>
</row>
<row>
<entry> <literal>/</literal> </entry>
<entry><literal>interval '1 hour' / int '3'</literal></entry>
<entry><literal>interval '00:20'</literal></entry>
<entry><literal>interval '1 hour' / double precision '1.5'</literal></entry>
<entry><literal>interval '00:40'</literal></entry>
</row>
</tbody>
</tgroup>
@ -4714,7 +4786,7 @@ substring('foobar' from 'o(.)b') <lineannotation>o</lineannotation>
linkend="functions-datetime-trunc">
</entry>
<entry><literal>date_trunc('hour', timestamp '2001-02-16 20:38:40')</literal></entry>
<entry><literal>2001-02-16 20:00:00+00</literal></entry>
<entry><literal>2001-02-16 20:00:00</literal></entry>
</row>
<row>
@ -4788,14 +4860,36 @@ substring('foobar' from 'o(.)b') <lineannotation>o</lineannotation>
<entry>Current date and time; see <xref
linkend="functions-datetime-current">
</entry>
<entry><literal>timeofday()</literal></entry>
<entry><literal>Wed Feb 21 17:01:13.000126 2001 EST</literal></entry>
<entry></entry>
<entry></entry>
</row>
</tbody>
</tgroup>
</table>
<para>
In addition to these functions, the SQL <literal>OVERLAPS</> keyword is
supported:
<synopsis>
( <replaceable>start1</replaceable>, <replaceable>end1</replaceable> ) OVERLAPS ( <replaceable>start2</replaceable>, <replaceable>end2</replaceable> )
( <replaceable>start1</replaceable>, <replaceable>length1</replaceable> ) OVERLAPS ( <replaceable>start2</replaceable>, <replaceable>length2</replaceable> )
</synopsis>
This expression yields true when two time periods (defined by their
endpoints) overlap, false when they do not overlap. The endpoints
can be specified as pairs of dates, times, or timestamps; or as
a date, time, or timestamp followed by an interval.
</para>
<screen>
SELECT (DATE '2001-02-16', DATE '2001-12-21') OVERLAPS
(DATE '2001-10-30', DATE '2002-10-30');
<lineannotation>Result: </lineannotation><computeroutput>true</computeroutput>
SELECT (DATE '2001-02-16', INTERVAL '100 days') OVERLAPS
(DATE '2001-10-30', DATE '2002-10-30');
<lineannotation>Result: </lineannotation><computeroutput>false</computeroutput>
</screen>
<sect2 id="functions-datetime-extract">
<title><function>EXTRACT</function>, <function>date_part</function></title>
@ -4906,8 +5000,8 @@ SELECT EXTRACT(DOY FROM TIMESTAMP '2001-02-16 20:38:40');
</para>
<screen>
SELECT EXTRACT(EPOCH FROM TIMESTAMP '2001-02-16 20:38:40');
<lineannotation>Result: </lineannotation><computeroutput>982352320</computeroutput>
SELECT EXTRACT(EPOCH FROM TIMESTAMP WITH TIME ZONE '2001-02-16 20:38:40-08');
<lineannotation>Result: </lineannotation><computeroutput>982384720</computeroutput>
SELECT EXTRACT(EPOCH FROM INTERVAL '5 days 3 hours');
<lineannotation>Result: </lineannotation><computeroutput>442800</computeroutput>
@ -5156,11 +5250,14 @@ SELECT date_part('hour', INTERVAL '4 hours 3 minutes');
date_trunc('<replaceable>field</replaceable>', <replaceable>source</replaceable>)
</synopsis>
<replaceable>source</replaceable> is a value expression of type
<type>timestamp</type>. (Values of type <type>date</type> and
<type>time</type> are cast automatically.)
<type>timestamp</type> or <type>interval</>.
(Values of type <type>date</type> and
<type>time</type> are cast automatically, to <type>timestamp</type> or
<type>interval</> respectively.)
<replaceable>field</replaceable> selects to which precision to
truncate the time stamp value. The return value is of type
<type>timestamp</type> with all fields that are less than the
truncate the input value. The return value is of type
<type>timestamp</type> or <type>interval</>
with all fields that are less significant than the
selected one set to zero (or one, for day and month).
</para>
@ -5185,10 +5282,10 @@ date_trunc('<replaceable>field</replaceable>', <replaceable>source</replaceable>
Examples:
<screen>
SELECT date_trunc('hour', TIMESTAMP '2001-02-16 20:38:40');
<lineannotation>Result: </lineannotation><computeroutput>2001-02-16 20:00:00+00</computeroutput>
<lineannotation>Result: </lineannotation><computeroutput>2001-02-16 20:00:00</computeroutput>
SELECT date_trunc('year', TIMESTAMP '2001-02-16 20:38:40');
<lineannotation>Result: </lineannotation><computeroutput>2001-01-01 00:00:00+00</computeroutput>
<lineannotation>Result: </lineannotation><computeroutput>2001-01-01 00:00:00</computeroutput>
</screen>
</para>
</sect2>

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