<!--

$Header: /cvsroot/pgsql/doc/src/sgml/datatype.sgml,v 1.79 2001/12/21 03:54:02 thomas Exp $

$Header: /cvsroot/pgsql/doc/src/sgml/datatype.sgml,v 1.80 2001/12/23 20:21:37 tgl Exp $

-->

<chapter id="datatype">

<entry>1 microsecond / 14 digits</entry>

</row>

<row>

<entry><type>interval</type></entry>

<entry><type>interval [ (<replaceable>p</replaceable>) ]</type></entry>

<entry>for time intervals</entry>

<entry>12 bytes</entry>

<entry>-178000000 years</entry>

</para>

<para>

<type>time</type> and <type>timestamp</type> both accept an

optional precision field <replaceable>p</replaceable> which

determines the number of digits retained beyond the seconds

decimal point. By default, there is no explicit bound on precision

and the actual precision is determined by the underlying double

precision floating point number used to store values in seconds

<type>time</type>, <type>timestamp</type>, and <type>interval</type>

accept an

optional precision value <replaceable>p</replaceable> which

specifies the number of fractional digits retained in the seconds

field. By default, there is no explicit bound on precision. The

effective limit of precision is determined by the underlying double

precision floating point number used to store values (in seconds

for <type>interval</type> and

in seconds since 2000-01-01 for <type>timestamp</type>.

in seconds since 2000-01-01 for <type>timestamp</type>). The

useful range of <replaceable>p</replaceable> is from 0 to about

6 for <type>timestamp</type>, but may be more for <type>interval</type>.

The system will accept <replaceable>p</replaceable> ranging from

0 to 13.

</para>

<para>

</sect3>

<sect3>

<title><type>interval</type></title>

<title><type>interval [ ( <replaceable>precision</replaceable> ) ]</type></title>

<indexterm>

<primary>interval</primary>

@ Quantity Unit [Quantity Unit...] [Direction]

</programlisting>

where: <literal>Quantity</literal> isan integer (possibly signed);

where: <literal>Quantity</literal> isa number (possibly signed),

<literal>Unit</literal> is <literal>second</literal>,

<literal>minute</literal>, <literal>hour</literal>, <literal>day</literal>,

<literal>week</literal>, <literal>month</literal>, <literal>year</literal>,

explicit unit markings. For example, <literal>'1 12:59:10'</> is read

the same as <literal>'1 day 12 hours 59 min 10 sec'</>.

</para>

<para>

The optional precision

<replaceable>p</replaceable> should be between 0 and 13, and

defaults to the precision of the input literal.

</para>

</sect3>

<sect3>