specifically, we can input either the "format with designators" or the
"alternative format", and we can output the former when IntervalStyle is set
to iso_8601.
Ron Mayer
where <replaceable>quantity</> is a number (possibly signed);
<replaceable>unit</> is <literal>microsecond</literal>,
@ -2384,6 +2384,76 @@ January 8 04:05:06 1999 PST
<varname>IntervalStyle</> is set to <literal>sql_standard</literal>.)
</para>
<para>
Interval values can also be written as ISO 8601 time intervals, using
either the <quote>format with designators</> of the standard's section
4.4.3.2 or the <quote>alternative format</> of section 4.4.3.3. The
format with designators looks like this:
<synopsis>
P <replaceable>quantity</> <replaceable>unit</> <optional> <replaceable>quantity</> <replaceable>unit</> ...</optional> <optional> T <optional> <replaceable>quantity</> <replaceable>unit</> ...</optional></optional>
</synopsis>
The string must start with a <literal>P</>, and may include a
<literal>T</> that introduces the time-of-day units. The
available unit abbreviations are given in <xref
linkend="datatype-interval-iso8601-units">. Units may be
omitted, and may be specified in any order, but units smaller than
a day must appear after <literal>T</>. In particular, the meaning of
<literal>M</> depends on whether it is before or after
<literal>T</>.
</para>
<table id="datatype-interval-iso8601-units">
<title>ISO 8601 interval unit abbreviations</title>
<tgroup cols="2">
<thead>
<row>
<entry>Abbreviation</entry>
<entry>Meaning</entry>
</row>
</thead>
<tbody>
<row>
<entry>Y</entry>
<entry>Years</entry>
</row>
<row>
<entry>M</entry>
<entry>Months (in the date part)</entry>
</row>
<row>
<entry>W</entry>
<entry>Weeks</entry>
</row>
<row>
<entry>D</entry>
<entry>Days</entry>
</row>
<row>
<entry>H</entry>
<entry>Hours</entry>
</row>
<row>
<entry>M</entry>
<entry>Minutes (in the time part)</entry>
</row>
<row>
<entry>S</entry>
<entry>Seconds</entry>
</row>
</tbody>
</tgroup>
</table>
<para>
In the alternative format:
<synopsis>
P <optional> <replaceable>years</>-<replaceable>months</>-<replaceable>days</> </optional> <optional> T <replaceable>hours</>:<replaceable>minutes</>:<replaceable>seconds</> </optional>
</synopsis>
the string must begin with <literal>P</literal>, and a
<literal>T</> separates the date and time parts of the interval.
The values are given as numbers similar to ISO 8601 dates.
</para>
<para>
When writing an interval constant with a <replaceable>fields</>
specification, or when assigning to an interval column that was defined
@ -2433,6 +2503,46 @@ January 8 04:05:06 1999 PST
For example, <literal>'1.5 month'</> becomes 1 month and 15 days.
Only seconds will ever be shown as fractional on output.
</para>
<para>
<xref linkend="datatype-interval-input-examples"> shows some examples
of valid <type>interval</> input.
</para>
<table id="datatype-interval-input-examples">
<title>Interval Input</title>
<tgroup cols="2">
<thead>
<row>
<entry>Example</entry>
<entry>Description</entry>
</row>
</thead>
<tbody>
<row>
<entry>1-2</entry>
<entry>SQL standard format: 1 year 2 months</entry>
</row>
<row>
<entry>3 4:05:06</entry>
<entry>SQL standard format: 3 days 4 hours 5 minutes 6 seconds</entry>
</row>
<row>
<entry>1 year 2 months 3 days 4 hours 5 minutes 6 seconds</entry>
<entry>Traditional Postgres format: 1 year 2 months 3 days 4 hours 5 minutes 6 seconds</entry>
</row>
<row>
<entry>P1Y2M3DT4H5M6S</entry>
<entry>ISO 8601 <quote>format with designators</>: same meaning as above</entry>
</row>
<row>
<entry>P0001-02-03T04:05:06</entry>
<entry>ISO 8601 <quote>alternative format</>: same meaning as above</entry>
</row>
</tbody>
</tgroup>
</table>
</sect2>
<sect2 id="datatype-interval-output">
@ -2446,8 +2556,8 @@ January 8 04:05:06 1999 PST
<para>
The output format of the interval type can be set to one of the
three styles <literal>sql_standard</>,
<literal>postgres</>, or <literal>postgres_verbose</>,
four styles <literal>sql_standard</>, <literal>postgres</>,
<literal>postgres_verbose</>, or <literal>iso_8601</>,
using the command <literal>SET intervalstyle</literal>.
The default is the <literal>postgres</> format.
<xref linkend="interval-style-output-table"> shows examples of each
@ -2476,6 +2586,12 @@ January 8 04:05:06 1999 PST
<varname>DateStyle</> parameter was set to non-<literal>ISO</> output.
</para>
<para>
The output of the <literal>iso_8601</> style matches the <quote>format
with designators</> described in section 4.4.3.2 of the
ISO 8601 standard.
</para>
<table id="interval-style-output-table">
<title>Interval Output Style Examples</title>
<tgroup cols="4">
@ -2506,6 +2622,12 @@ January 8 04:05:06 1999 PST
<entry>@ 3 days 4 hours 5 mins 6 secs</entry>
<entry>@ 1 year 2 mons -3 days 4 hours 5 mins 6 secs ago</entry>
2 years | 2 years 10 mons | 2 years 10 mons 15 days | 2 years 00:00:01 | 2 years 10 mons 00:00:01 | 2 years 10 mons 15 days 00:00:01 | 10:00:00 | 10:30:00
Tom Lane
17 years ago