<!--

$Header: /cvsroot/pgsql/doc/src/sgml/datatype.sgml,v 1.28 2000/04/13 21:44:25 momjian Exp $

$Header: /cvsroot/pgsql/doc/src/sgml/datatype.sgml,v 1.29 2000/04/14 15:08:56 thomas Exp $

-->

<chapter id="datatype">

<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>,

<literal>decade</literal>, <literal>century</literal>, <literal>millenium</literal>,

<literal>decade</literal>, <literal>century</literal>, <literal>millennium</literal>,

or abbreviations or plurals of these units;

<literal>Direction</literal> can be <literal>ago</literal> or

empty.

For the

<function>date_part</function> and <function>date_trunc</function>

functions, arguments can be

`year', `month', `day', `hour', `minute', and `second',

`<literal>year</literal>', `<literal>month</literal>',

`<literal>day</literal>', `<literal>hour</literal>',

`<literal>minute</literal>', and `<literal>second</literal>',

as well as the more specialized quantities

`decade', `century', `millenium', `millisecond', and `microsecond'.

<function>date_part</function> allows `dow'

to return day of week and `epoch' to return seconds since 1970

(for <type>timestamp</type>)

or 'epoch' to return total elapsed seconds (for <type>interval</type>).

`<literal>decade</literal>', `<literal>century</literal>',

`<literal>millennium</literal>', `<literal>millisecond</literal>',

and `<literal>microsecond</literal>'.

<function>date_part</function> allows `<literal>dow</literal>'

to return day of week, '<literal>week</literal>' to return the

ISO-defined week of year, and `<literal>epoch</literal>' to return

seconds since 1970 (for <type>timestamp</type>)

or '<literal>epoch</literal>' to return total elapsed seconds

(for <type>interval</type>).

</para>

</sect1>

<para>

All templates allow the use of prefix and suffix modifiers. Modifiers are

always valid for use in templates. The prefix 'FX' is a global modifier only.

always valid for use in templates. The prefix

'<literal>FX</literal>' is a global modifier only.

</para>

<para>