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Add more complete details on date/time keywords and parsing rules.
Move some tabular information on these from the chapter on data types to the appendix on dates and times.
This commit is contained in:
Thomas G. Lockhart
parent
c826d1cefb
commit
c5c28ed06a
@ -1,5 +1,5 @@
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<!--
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$Header: /cvsroot/pgsql/doc/src/sgml/datatype.sgml,v 1.81 2001/12/29 18:35:46 thomas Exp $
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$Header: /cvsroot/pgsql/doc/src/sgml/datatype.sgml,v 1.82 2002/01/04 17:02:02 thomas Exp $
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-->
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<chapter id="datatype">
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@ -1346,29 +1346,35 @@ SELECT b, char_length(b) FROM test2;
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<para>
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Time zones, and time-zone conventions, are influenced by
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political decisions, not just geometry. Time zones around the
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political decisions, not just earth geometry. Time zones around the
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world became somewhat standardized during the 1900's,
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but continue to be prone to arbitrary changes.
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<productname>PostgreSQL</productname> uses your operating
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system's underlying features to provide time-zone
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system's underlying features to provide output time-zone
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support, and these systems usually contain information for only
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the time period 1902 through 2038 (corresponding to the full
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range of conventional Unix system time).
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<type>timestamp with time zone</type> will use time zone
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information only within that year range, and assumes that times
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are in UTC outside that range.
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<type>timestamp with time zone</type> and <type>time with time
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zone</type> will use time zone
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information only within that year range, and assume that times
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outside that range are in <acronym>UTC</acronym>.
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</para>
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<para>
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To ensure compatibility to earlier versions of
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<productname>PostgreSQL</productname>
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we continue to provide <type>datetime</type>
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To ensure an upgrade path from versions of
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<productname>PostgreSQL</productname> earlier than 7.0,
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we recognize <type>datetime</type>
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(equivalent to <type>timestamp</type>) and
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<type>timespan</type> (equivalent to <type>interval</type>),
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however support for these is now restricted to having an
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<type>timespan</type> (equivalent to <type>interval</type>).
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These types are
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now restricted to having an
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implicit translation to <type>timestamp</type> and
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<type>interval</type>, and these name mappings will be removed in
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the next version.
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<type>interval</type>, and
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support for these will be removed in the next release of
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<productname>PostgreSQL</productname> (likely named 7.3).
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</para>
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<para>
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The types <type>abstime</type>
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and <type>reltime</type> are lower precision types which are used internally.
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You are discouraged from using any of these types in new
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@ -1402,7 +1408,8 @@ SELECT b, char_length(b) FROM test2;
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<acronym>SQL</acronym> standard requires.
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See <xref linkend="datetime-appendix">
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for the exact parsing rules of date/time input and for the
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recognized time zones.
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recognized text fields including months, days of the week, and
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time zones.
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</para>
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<para>
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@ -1431,7 +1438,7 @@ SELECT b, char_length(b) FROM test2;
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</indexterm>
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<para>
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The following are possible inputs for the <type>date</type> type.
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The following are some possible inputs for the <type>date</type> type.
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<table tocentry="1">
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<title>Date Input</title>
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@ -1479,6 +1486,10 @@ SELECT b, char_length(b) FROM test2;
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<entry>99008</entry>
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<entry>Year and day of year</entry>
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</row>
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<row>
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<entry>J2451187</entry>
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<entry>Julian day</entry>
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</row>
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<row>
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<entry>January 8, 99 BC</entry>
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<entry>Year 99 before the Common Era</entry>
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@ -1487,116 +1498,6 @@ SELECT b, char_length(b) FROM test2;
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</tgroup>
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</table>
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</para>
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<para>
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<table tocentry="1">
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<title>Month Abbreviations</title>
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<tgroup cols="2">
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<thead>
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<row>
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<entry>Month</entry>
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<entry>Abbreviations</entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry>April</entry>
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<entry>Apr</entry>
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</row>
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<row>
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<entry>August</entry>
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<entry>Aug</entry>
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</row>
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<row>
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<entry>December</entry>
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<entry>Dec</entry>
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</row>
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<row>
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<entry>February</entry>
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<entry>Feb</entry>
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</row>
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<row>
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<entry>January</entry>
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<entry>Jan</entry>
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</row>
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<row>
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<entry>July</entry>
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<entry>Jul</entry>
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</row>
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<row>
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<entry>June</entry>
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<entry>Jun</entry>
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</row>
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<row>
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<entry>March</entry>
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<entry>Mar</entry>
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</row>
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<row>
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<entry>November</entry>
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<entry>Nov</entry>
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</row>
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<row>
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<entry>October</entry>
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<entry>Oct</entry>
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</row>
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<row>
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<entry>September</entry>
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<entry>Sep, Sept</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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<note>
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<para>
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The month <literal>May</literal> has no explicit abbreviation, for obvious reasons.
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</para>
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</note>
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</para>
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<para>
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<table tocentry="1">
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<title>Day of the Week Abbreviations</title>
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<tgroup cols="2">
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<thead>
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<row>
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<entry>Day</entry>
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<entry>Abbreviation</entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry>Sunday</entry>
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<entry>Sun</entry>
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</row>
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<row>
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<entry>Monday</entry>
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<entry>Mon</entry>
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</row>
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<row>
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<entry>Tuesday</entry>
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<entry>Tue, Tues</entry>
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</row>
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<row>
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<entry>Wednesday</entry>
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<entry>Wed, Weds</entry>
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</row>
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<row>
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<entry>Thursday</entry>
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<entry>Thu, Thur, Thurs</entry>
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</row>
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<row>
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<entry>Friday</entry>
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<entry>Fri</entry>
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</row>
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<row>
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<entry>Saturday</entry>
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<entry>Sat</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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</sect3>
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<sect3>
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@ -1655,14 +1556,6 @@ SELECT b, char_length(b) FROM test2;
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<entry>04:05 PM</entry>
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<entry>Same as 16:05; input hour must be <= 12</entry>
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</row>
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<row>
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<entry>z</entry>
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<entry>Same as 00:00:00</entry>
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</row>
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<row>
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<entry>zulu</entry>
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<entry>Same as 00:00:00</entry>
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</row>
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<row>
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<entry>allballs</entry>
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<entry>Same as 00:00:00</entry>
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@ -1,11 +1,197 @@
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<!--
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$Header: /cvsroot/pgsql/doc/src/sgml/datetime.sgml,v 2.24 2001/12/29 18:35:47 thomas Exp $
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$Header: /cvsroot/pgsql/doc/src/sgml/datetime.sgml,v 2.25 2002/01/04 17:02:25 thomas Exp $
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Date/time details
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-->
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<appendix id="datetime-appendix">
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<title id="datetime-appendix-title">Date/Time Support</title>
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<para>
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<productname>PostgreSQL</productname> uses an internal heuristic
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parser for all date/time support. Dates and times are input as
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strings, and are broken up into distinct fields with a preliminary
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determination of what kind of information may be in the
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field. Each field is interpreted and either assigned a numeric
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value, ignored, or rejected.
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The parser contains internal lookup tables for all textual fields,
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including months, days of the week, and time
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zones.
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</para>
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<para>
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This appendix includes information on the content of these
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lookup tables and describes the steps used by the parser to decode
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dates and times.
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</para>
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<sect1>
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<title>Date/Time Keywords</title>
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<para>
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<table tocentry="1">
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<title>Month Abbreviations</title>
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<tgroup cols="2">
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<thead>
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<row>
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<entry>Month</entry>
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<entry>Abbreviations</entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry>April</entry>
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<entry>Apr</entry>
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</row>
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<row>
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<entry>August</entry>
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<entry>Aug</entry>
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</row>
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<row>
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<entry>December</entry>
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<entry>Dec</entry>
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</row>
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<row>
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<entry>February</entry>
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<entry>Feb</entry>
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</row>
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<row>
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<entry>January</entry>
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<entry>Jan</entry>
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</row>
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<row>
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<entry>July</entry>
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<entry>Jul</entry>
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</row>
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<row>
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<entry>June</entry>
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<entry>Jun</entry>
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</row>
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<row>
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<entry>March</entry>
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<entry>Mar</entry>
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</row>
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<row>
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<entry>November</entry>
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<entry>Nov</entry>
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</row>
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<row>
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<entry>October</entry>
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<entry>Oct</entry>
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</row>
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<row>
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<entry>September</entry>
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<entry>Sep, Sept</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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<note>
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<para>
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The month <literal>May</literal> has no explicit abbreviation, for obvious reasons.
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</para>
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</note>
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</para>
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<para>
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<table tocentry="1">
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<title>Day of the Week Abbreviations</title>
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<tgroup cols="2">
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<thead>
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<row>
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<entry>Day</entry>
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<entry>Abbreviation</entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry>Sunday</entry>
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<entry>Sun</entry>
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</row>
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<row>
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<entry>Monday</entry>
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<entry>Mon</entry>
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</row>
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<row>
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<entry>Tuesday</entry>
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<entry>Tue, Tues</entry>
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</row>
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<row>
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<entry>Wednesday</entry>
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<entry>Wed, Weds</entry>
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</row>
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<row>
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<entry>Thursday</entry>
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<entry>Thu, Thur, Thurs</entry>
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</row>
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<row>
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<entry>Friday</entry>
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<entry>Fri</entry>
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</row>
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<row>
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<entry>Saturday</entry>
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<entry>Sat</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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<para>
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<table tocentry="1">
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<title><productname>PostgreSQL</productname> Field Modifiers</title>
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<titleabbrev>Field Modifiers</titleabbrev>
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<tgroup cols="2">
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<thead>
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<row>
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<entry>Identifier</entry>
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<entry>Description</entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry>ABSTIME</entry>
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<entry>Keyword ignored</entry>
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</row>
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<row>
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<entry>AM</entry>
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<entry>Time is before 12:00</entry>
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</row>
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<row>
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<entry>AT</entry>
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<entry>Keyword ignored</entry>
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</row>
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<row>
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<entry>JULIAN, JD, J</entry>
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<entry>Next field is Julian Day</entry>
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</row>
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<row>
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<entry>ON</entry>
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<entry>Keyword ignored</entry>
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</row>
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<row>
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<entry>PM</entry>
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<entry>Time is on or after after 12:00</entry>
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</row>
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<row>
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<entry>T</entry>
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<entry>Next field is time</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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<para>
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The keyword <literal>ABSTIME</literal> is ignored for historical
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reasons; in very old releases of
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<productname>PostgreSQL</productname> invalid <type>ABSTIME</type>
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fields were emitted as <quote>Invalid Abstime</quote>. This is no
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longer the case however and this keyword will likely be dropped in
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a future release.
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</para>
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</sect1>
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<sect1 id="timezones">
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<title>Time Zones</title>
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@ -19,6 +205,15 @@ Date/time details
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system interface to provide access to general, cross-timezone
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information. The underlying OS <emphasis>is</emphasis> used to
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provide time zone information for <emphasis>output</emphasis>, however.
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</para>
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<para>
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The following table of time zones recognized by
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<productname>PostgreSQL</productname> is organized by time
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zone offset from UTC, rather than alphabetically; this is intended
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to faciliate
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matching local usage with recognized abreviations for cases where
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these might differ.
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<table tocentry="1">
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<title><productname>PostgreSQL</productname> Recognized Time Zones</title>
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@ -360,6 +555,26 @@ Date/time details
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<entry>+00:00</entry>
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<entry>Greenwich Mean Time</entry>
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</row>
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<row>
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<entry>UT</entry>
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<entry>+00:00</entry>
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<entry>Universal Time</entry>
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</row>
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<row>
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<entry>UTC</entry>
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<entry>+00:00</entry>
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<entry>Universal Time, Coordinated</entry>
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</row>
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<row>
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<entry>Z</entry>
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<entry>+00:00</entry>
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<entry>Same as UTC</entry>
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</row>
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<row>
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<entry>ZULU</entry>
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<entry>+00:00</entry>
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<entry>Same as UTC</entry>
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</row>
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<row>
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<entry>WET</entry>
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<entry>+00:00</entry>
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@ -603,13 +818,15 @@ Date/time details
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<substeps>
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<step>
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<para>
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If the token contains a colon (":"), this is a time string.
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If the numeric token contains a colon (":"), this is a time
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string. Include all subsequent digits and colons.
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</para>
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</step>
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<step>
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<para>
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If the token contains a dash ("-"), slash ("/"), or dot ("."),
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If the numeric token contains a dash ("-"), slash ("/"), or
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two or more dots ("."),
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this is a date string which may have a text month.
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</para>
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</step>
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@ -617,7 +834,8 @@ Date/time details
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<step>
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<para>
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If the token is numeric only, then it is either a single field
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or an ISO-8601 concatenated date (e.g. <literal>19990113</literal> for January 13, 1999)
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or an ISO-8601 concatenated date
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(e.g. <literal>19990113</literal> for January 13, 1999)
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or time (e.g. 141516 for 14:15:16).
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</para>
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</step>
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@ -689,6 +907,13 @@ Date/time details
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</para>
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</step>
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<step>
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<para>
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If four or six digits and a year has already been read, then
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interpret as a time.
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</para>
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</step>
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<step>
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<para>
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If four or more digits, then interpret as a year.
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@ -732,10 +957,10 @@ Date/time details
|
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<step>
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<para>
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If BC has been specified, negate the year and offset by one for
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If BC has been specified, negate the year and add one for
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internal storage
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(there is no year zero in the Gregorian calendar, so numerically
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1BC becomes year zero).
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<literal>1BC</literal> becomes year zero).
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</para>
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||||
</step>
|
||||
|
||||
|
||||
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Reference in New Issue
Block a user