doc/src/sgml/func/func-formatting.sgml - master - githubmirror/postgres

doc/src/sgml/func/func-formatting.sgml
1 197 строк45 KB
Bruce Momjian
doc: clarify to_char("OF") HH/MM doesn't represent actual chars
21 июл 2026, 18:59
21 июл 2026, 18:5985df8c5
  <sect1 id="functions-formatting">
   <title>Data Type Formatting Functions</title>

   <indexterm>
    <primary>formatting</primary>
   </indexterm>

   <para>
    The <productname>PostgreSQL</productname> formatting functions
    provide a powerful set of tools for converting various data types
    (date/time, integer, floating point, numeric) to formatted strings
    and for converting from formatted strings to specific data types.
    <xref linkend="functions-formatting-table"/> lists them.
    These functions all follow a common calling convention: the first
    argument is the value to be formatted and the second argument is a
    template that defines the output or input format.
   </para>

   <table id="functions-formatting-table">
    <title>Formatting Functions</title>
    <tgroup cols="1">
     <thead>
      <row>
       <entry role="func_table_entry"><para role="func_signature">
        Function
       </para>
       <para>
        Description
       </para>
       <para>
        Example(s)
       </para></entry>
      </row>
     </thead>

     <tbody>
      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <indexterm>
         <primary>to_char</primary>
        </indexterm>
        <function>to_char</function> ( <type>timestamp</type>, <type>text</type> )
        <returnvalue>text</returnvalue>
       </para>
       <para role="func_signature">
        <function>to_char</function> ( <type>timestamp with time zone</type>, <type>text</type> )
        <returnvalue>text</returnvalue>
       </para>
       <para>
        Converts time stamp to string according to the given format.
       </para>
       <para>
        <literal>to_char(timestamp '2002-04-20 17:31:12.66', 'HH12:MI:SS')</literal>
        <returnvalue>05:31:12</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <function>to_char</function> ( <type>interval</type>, <type>text</type> )
        <returnvalue>text</returnvalue>
       </para>
       <para>
        Converts interval to string according to the given format.
       </para>
       <para>
       <literal>to_char(interval '15h 2m 12s', 'HH24:MI:SS')</literal>
       <returnvalue>15:02:12</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <function>to_char</function> ( <replaceable>numeric_type</replaceable>, <type>text</type> )
        <returnvalue>text</returnvalue>
       </para>
       <para>
        Converts number to string according to the given format; available
        for <type>integer</type>, <type>bigint</type>, <type>numeric</type>,
        <type>real</type>, <type>double precision</type>.
       </para>
       <para>
        <literal>to_char(125, '999')</literal>
        <returnvalue>125</returnvalue>
       </para>
       <para>
        <literal>to_char(125.8::real, '999D9')</literal>
        <returnvalue>125.8</returnvalue>
       </para>
       <para>
        <literal>to_char(-125.8, '999D99S')</literal>
        <returnvalue>125.80-</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <indexterm>
         <primary>to_date</primary>
        </indexterm>
        <function>to_date</function> ( <type>text</type>, <type>text</type> )
        <returnvalue>date</returnvalue>
       </para>
       <para>
        Converts string to date according to the given format.
       </para>
       <para>
        <literal>to_date('05 Dec 2000', 'DD Mon YYYY')</literal>
        <returnvalue>2000-12-05</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <indexterm>
         <primary>to_number</primary>
        </indexterm>
        <function>to_number</function> ( <type>text</type>, <type>text</type> )
        <returnvalue>numeric</returnvalue>
       </para>
       <para>
        Converts string to numeric according to the given format.
       </para>
       <para>
        <literal>to_number('12,454.8-', '99G999D9S')</literal>
        <returnvalue>-12454.8</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <indexterm>
         <primary>to_timestamp</primary>
        </indexterm>
        <function>to_timestamp</function> ( <type>text</type>, <type>text</type> )
        <returnvalue>timestamp with time zone</returnvalue>
       </para>
       <para>
        Converts string to time stamp according to the given format.
        (See also <function>to_timestamp(double precision)</function> in
        <xref linkend="functions-datetime-table"/>.)
       </para>
       <para>
        <literal>to_timestamp('05 Dec 2000', 'DD Mon YYYY')</literal>
        <returnvalue>2000-12-05 00:00:00-05</returnvalue>
       </para></entry>
      </row>
     </tbody>
    </tgroup>
   </table>

   <tip>
    <para>
     <function>to_timestamp</function> and <function>to_date</function>
     exist to handle input formats that cannot be converted by
     simple casting.  For most standard date/time formats, simply casting the
     source string to the required data type works, and is much easier.
     Similarly, <function>to_number</function> is unnecessary for standard numeric
     representations.
    </para>
   </tip>

   <para>
    In a <function>to_char</function> output template string, there are certain
    patterns that are recognized and replaced with appropriately-formatted
    data based on the given value.  Any text that is not a template pattern is
    simply copied verbatim.  Similarly, in an input template string (for the
    other functions), template patterns identify the values to be supplied by
    the input data string.  If there are characters in the template string
    that are not template patterns, the corresponding characters in the input
    data string are simply skipped over (whether or not they are equal to the
    template string characters).
   </para>

  <para>
   <xref linkend="functions-formatting-datetime-table"/> shows the
   template patterns available for formatting date and time values.
  </para>

    <table id="functions-formatting-datetime-table">
     <title>Template Patterns for Date/Time Formatting</title>
     <tgroup cols="2">
      <colspec colname="col1" colwidth="1*"/>
      <colspec colname="col2" colwidth="3*"/>
      <thead>
       <row>
        <entry>Pattern</entry>
        <entry>Description</entry>
       </row>
      </thead>
      <tbody>
       <row>
        <entry><literal>HH</literal></entry>
        <entry>hour of day (01&ndash;12)</entry>
       </row>
       <row>
        <entry><literal>HH12</literal></entry>
        <entry>hour of day (01&ndash;12)</entry>
       </row>
       <row>
        <entry><literal>HH24</literal></entry>
        <entry>hour of day (00&ndash;23)</entry>
       </row>
       <row>
        <entry><literal>MI</literal></entry>
        <entry>minute (00&ndash;59)</entry>
       </row>
       <row>
        <entry><literal>SS</literal></entry>
        <entry>second (00&ndash;59)</entry>
       </row>
       <row>
        <entry><literal>MS</literal></entry>
        <entry>millisecond (000&ndash;999)</entry>
       </row>
       <row>
        <entry><literal>US</literal></entry>
        <entry>microsecond (000000&ndash;999999)</entry>
       </row>
       <row>
        <entry><literal>FF1</literal></entry>
        <entry>tenth of second (0&ndash;9)</entry>
       </row>
       <row>
        <entry><literal>FF2</literal></entry>
        <entry>hundredth of second (00&ndash;99)</entry>
       </row>
       <row>
        <entry><literal>FF3</literal></entry>
        <entry>millisecond (000&ndash;999)</entry>
       </row>
       <row>
        <entry><literal>FF4</literal></entry>
        <entry>tenth of a millisecond (0000&ndash;9999)</entry>
       </row>
       <row>
        <entry><literal>FF5</literal></entry>
        <entry>hundredth of a millisecond (00000&ndash;99999)</entry>
       </row>
       <row>
        <entry><literal>FF6</literal></entry>
        <entry>microsecond (000000&ndash;999999)</entry>
       </row>
       <row>
        <entry><literal>SSSS</literal>, <literal>SSSSS</literal></entry>
        <entry>seconds past midnight (0&ndash;86399)</entry>
       </row>
       <row>
        <entry><literal>AM</literal>, <literal>am</literal>,
        <literal>PM</literal> or <literal>pm</literal></entry>
        <entry>meridiem indicator (without periods)</entry>
       </row>
       <row>
        <entry><literal>A.M.</literal>, <literal>a.m.</literal>,
        <literal>P.M.</literal> or <literal>p.m.</literal></entry>
        <entry>meridiem indicator (with periods)</entry>
       </row>
       <row>
        <entry><literal>Y,YYY</literal></entry>
        <entry>year (4 or more digits) with comma</entry>
       </row>
       <row>
        <entry><literal>YYYY</literal></entry>
        <entry>year (4 or more digits)</entry>
       </row>
       <row>
        <entry><literal>YYY</literal></entry>
        <entry>last 3 digits of year</entry>
       </row>
       <row>
        <entry><literal>YY</literal></entry>
        <entry>last 2 digits of year</entry>
       </row>
       <row>
        <entry><literal>Y</literal></entry>
        <entry>last digit of year</entry>
       </row>
       <row>
        <entry><literal>IYYY</literal></entry>
        <entry>ISO 8601 week-numbering year (4 or more digits)</entry>
       </row>
       <row>
        <entry><literal>IYY</literal></entry>
        <entry>last 3 digits of ISO 8601 week-numbering year</entry>
       </row>
       <row>
        <entry><literal>IY</literal></entry>
        <entry>last 2 digits of ISO 8601 week-numbering year</entry>
       </row>
       <row>
        <entry><literal>I</literal></entry>
        <entry>last digit of ISO 8601 week-numbering year</entry>
       </row>
       <row>
        <entry><literal>BC</literal>, <literal>bc</literal>,
        <literal>AD</literal> or <literal>ad</literal></entry>
        <entry>era indicator (without periods)</entry>
       </row>
       <row>
        <entry><literal>B.C.</literal>, <literal>b.c.</literal>,
        <literal>A.D.</literal> or <literal>a.d.</literal></entry>
        <entry>era indicator (with periods)</entry>
       </row>
       <row>
        <entry><literal>MONTH</literal></entry>
        <entry>full upper case month name (blank-padded to 9 chars)</entry>
       </row>
       <row>
        <entry><literal>Month</literal></entry>
        <entry>full capitalized month name (blank-padded to 9 chars)</entry>
       </row>
       <row>
        <entry><literal>month</literal></entry>
        <entry>full lower case month name (blank-padded to 9 chars)</entry>
       </row>
       <row>
        <entry><literal>MON</literal></entry>
        <entry>abbreviated upper case month name (3 chars in English, localized lengths vary)</entry>
       </row>
       <row>
        <entry><literal>Mon</literal></entry>
        <entry>abbreviated capitalized month name (3 chars in English, localized lengths vary)</entry>
       </row>
       <row>
        <entry><literal>mon</literal></entry>
        <entry>abbreviated lower case month name (3 chars in English, localized lengths vary)</entry>
       </row>
       <row>
        <entry><literal>MM</literal></entry>
        <entry>month number (01&ndash;12)</entry>
       </row>
       <row>
        <entry><literal>DAY</literal></entry>
        <entry>full upper case day name (blank-padded to 9 chars)</entry>
       </row>
       <row>
        <entry><literal>Day</literal></entry>
        <entry>full capitalized day name (blank-padded to 9 chars)</entry>
       </row>
       <row>
        <entry><literal>day</literal></entry>
        <entry>full lower case day name (blank-padded to 9 chars)</entry>
       </row>
       <row>
        <entry><literal>DY</literal></entry>
        <entry>abbreviated upper case day name (3 chars in English, localized lengths vary)</entry>
       </row>
       <row>
        <entry><literal>Dy</literal></entry>
        <entry>abbreviated capitalized day name (3 chars in English, localized lengths vary)</entry>
       </row>
       <row>
        <entry><literal>dy</literal></entry>
        <entry>abbreviated lower case day name (3 chars in English, localized lengths vary)</entry>
       </row>
       <row>
        <entry><literal>DDD</literal></entry>
        <entry>day of year (001&ndash;366)</entry>
       </row>
       <row>
        <entry><literal>IDDD</literal></entry>
        <entry>day of ISO 8601 week-numbering year (001&ndash;371; day 1 of the year is Monday of the first ISO week)</entry>
       </row>
       <row>
        <entry><literal>DD</literal></entry>
        <entry>day of month (01&ndash;31)</entry>
       </row>
       <row>
        <entry><literal>D</literal></entry>
        <entry>day of the week, Sunday (<literal>1</literal>) to Saturday (<literal>7</literal>)</entry>
       </row>
       <row>
        <entry><literal>ID</literal></entry>
        <entry>ISO 8601 day of the week, Monday (<literal>1</literal>) to Sunday (<literal>7</literal>)</entry>
       </row>
       <row>
        <entry><literal>W</literal></entry>
        <entry>week of month (1&ndash;5) (the first week starts on the first day of the month)</entry>
       </row>
       <row>
        <entry><literal>WW</literal></entry>
        <entry>week number of year (1&ndash;53) (the first week starts on the first day of the year)</entry>
       </row>
       <row>
        <entry><literal>IW</literal></entry>
        <entry>week number of ISO 8601 week-numbering year (01&ndash;53; the first Thursday of the year is in week 1)</entry>
       </row>
       <row>
        <entry><literal>CC</literal></entry>
        <entry>century (2 digits) (the twenty-first century starts on 2001-01-01)</entry>
       </row>
       <row>
        <entry><literal>J</literal></entry>
        <entry>Julian Date (integer days since November 24, 4714 BC at local
        midnight; see <xref linkend="datetime-julian-dates"/>)</entry>
       </row>
       <row>
        <entry><literal>Q</literal></entry>
        <entry>quarter</entry>
       </row>
       <row>
        <entry><literal>RM</literal></entry>
        <entry>month in upper case Roman numerals (I&ndash;XII; I=January)</entry>
       </row>
       <row>
        <entry><literal>rm</literal></entry>
        <entry>month in lower case Roman numerals (i&ndash;xii; i=January)</entry>
       </row>
       <row>
        <entry><literal>TZ</literal></entry>
        <entry>upper case time-zone abbreviation</entry>
       </row>
       <row>
        <entry><literal>tz</literal></entry>
        <entry>lower case time-zone abbreviation</entry>
       </row>
       <row>
       <entry><literal>TZH</literal></entry>
        <entry>time-zone hours</entry>
       </row>
       <row>
       <entry><literal>TZM</literal></entry>
        <entry>time-zone minutes</entry>
       </row>
       <row>
        <entry><literal>OF</literal></entry>
        <entry>time-zone offset from UTC (<replaceable>hh</replaceable>
         or <replaceable>hh</replaceable><literal>:</literal><replaceable>mi</replaceable>)</entry>
       </row>
      </tbody>
     </tgroup>
    </table>

   <para>
    Modifiers can be applied to any template pattern to alter its
    behavior.  For example, <literal>FMMonth</literal>
    is the <literal>Month</literal> pattern with the
    <literal>FM</literal> modifier.
    <xref linkend="functions-formatting-datetimemod-table"/> shows the
    modifier patterns for date/time formatting.
   </para>

    <table id="functions-formatting-datetimemod-table">
     <title>Template Pattern Modifiers for Date/Time Formatting</title>
     <tgroup cols="3">
      <thead>
       <row>
        <entry>Modifier</entry>
        <entry>Description</entry>
        <entry>Example</entry>
       </row>
      </thead>
      <tbody>
       <row>
        <entry><literal>FM</literal> prefix</entry>
        <entry>fill mode (suppress leading zeroes and padding blanks)</entry>
        <entry><literal>FMMonth</literal></entry>
       </row>
       <row>
        <entry><literal>TH</literal> suffix</entry>
        <entry>upper case ordinal number suffix</entry>
        <entry><literal>DDTH</literal>, e.g., <literal>12TH</literal></entry>
       </row>
       <row>
        <entry><literal>th</literal> suffix</entry>
        <entry>lower case ordinal number suffix</entry>
        <entry><literal>DDth</literal>, e.g., <literal>12th</literal></entry>
       </row>
       <row>
        <entry><literal>FX</literal> prefix</entry>
        <entry>fixed format global option (see usage notes)</entry>
        <entry><literal>FX&nbsp;Month&nbsp;DD&nbsp;Day</literal></entry>
       </row>
       <row>
        <entry><literal>TM</literal> prefix</entry>
        <entry>translation mode (use localized day and month names based on
         <xref linkend="guc-lc-time"/>)</entry>
        <entry><literal>TMMonth</literal></entry>
       </row>
       <row>
        <entry><literal>SP</literal> suffix</entry>
        <entry>spell mode (not implemented)</entry>
        <entry><literal>DDSP</literal></entry>
       </row>
      </tbody>
     </tgroup>
    </table>

   <para>
    Usage notes for date/time formatting:

    <itemizedlist>
     <listitem>
      <para>
       <literal>FM</literal> suppresses leading zeroes and trailing blanks
       that would otherwise be added to make the output of a pattern be
       fixed-width.  In <productname>PostgreSQL</productname>,
       <literal>FM</literal> modifies only the next specification, while in
       Oracle <literal>FM</literal> affects all subsequent
       specifications, and repeated <literal>FM</literal> modifiers
       toggle fill mode on and off.
      </para>
     </listitem>

     <listitem>
      <para>
       <literal>TM</literal> suppresses trailing blanks whether or
       not <literal>FM</literal> is specified.
      </para>
     </listitem>

     <listitem>
      <para>
       <function>to_timestamp</function> and <function>to_date</function>
       ignore letter case in the input; so for
       example <literal>MON</literal>, <literal>Mon</literal>,
       and <literal>mon</literal> all accept the same strings.  When using
       the <literal>TM</literal> modifier, case-folding is done according to
       the rules of the function's input collation (see
       <xref linkend="collation"/>).
      </para>
     </listitem>

     <listitem>
      <para>
       <function>to_timestamp</function> and <function>to_date</function>
       skip multiple blank spaces at the beginning of the input string and
       around date and time values unless the <literal>FX</literal> option is used.  For example,
       <literal>to_timestamp('&nbsp;2000&nbsp;&nbsp;&nbsp;&nbsp;JUN', 'YYYY MON')</literal> and
       <literal>to_timestamp('2000 - JUN', 'YYYY-MON')</literal> work, but
       <literal>to_timestamp('2000&nbsp;&nbsp;&nbsp;&nbsp;JUN', 'FXYYYY MON')</literal> returns an error
       because <function>to_timestamp</function> expects only a single space.
       <literal>FX</literal> must be specified as the first item in
       the template.
      </para>
     </listitem>

     <listitem>
      <para>
       A separator (a space or non-letter/non-digit character) in the template string of
       <function>to_timestamp</function> and <function>to_date</function>
       matches any single separator in the input string or is skipped,
       unless the <literal>FX</literal> option is used.
       For example, <literal>to_timestamp('2000JUN', 'YYYY///MON')</literal> and
       <literal>to_timestamp('2000/JUN', 'YYYY MON')</literal> work, but
       <literal>to_timestamp('2000//JUN', 'YYYY/MON')</literal>
       returns an error because the number of separators in the input string
       exceeds the number of separators in the template.
      </para>
      <para>
       If <literal>FX</literal> is specified, a separator in the template string
       matches exactly one character in the input string.  But note that the
       input string character is not required to be the same as the separator from the template string.
       For example, <literal>to_timestamp('2000/JUN', 'FXYYYY MON')</literal>
       works, but <literal>to_timestamp('2000/JUN', 'FXYYYY&nbsp;&nbsp;MON')</literal>
       returns an error because the second space in the template string consumes
       the letter <literal>J</literal> from the input string.
      </para>
     </listitem>

     <listitem>
      <para>
       A <literal>TZH</literal> template pattern can match a signed number.
       Without the <literal>FX</literal> option, minus signs may be ambiguous,
       and could be interpreted as a separator.
       This ambiguity is resolved as follows:  If the number of separators before
       <literal>TZH</literal> in the template string is less than the number of
       separators before the minus sign in the input string, the minus sign
       is interpreted as part of <literal>TZH</literal>.
       Otherwise, the minus sign is considered to be a separator between values.
       For example, <literal>to_timestamp('2000 -10', 'YYYY TZH')</literal> matches
       <literal>-10</literal> to <literal>TZH</literal>, but
       <literal>to_timestamp('2000 -10', 'YYYY&nbsp;&nbsp;TZH')</literal>
       matches <literal>10</literal> to <literal>TZH</literal>.
      </para>
     </listitem>

     <listitem>
      <para>
       Ordinary text is allowed in <function>to_char</function>
       templates and will be output literally.  You can put a substring
       in double quotes to force it to be interpreted as literal text
       even if it contains template patterns.  For example, in
       <literal>'"Hello Year "YYYY'</literal>, the <literal>YYYY</literal>
       will be replaced by the year data, but the single <literal>Y</literal> in <literal>Year</literal>
       will not be.
       In <function>to_date</function>, <function>to_number</function>,
       and <function>to_timestamp</function>, literal text and double-quoted
       strings result in skipping the number of characters contained in the
       string; for example <literal>"XX"</literal> skips two input characters
       (whether or not they are <literal>XX</literal>).
      </para>
      <tip>
        <para>
          Prior to <productname>PostgreSQL</productname> 12, it was possible to
          skip arbitrary text in the input string using non-letter or non-digit
          characters. For example,
          <literal>to_timestamp('2000y6m1d', 'yyyy-MM-DD')</literal> used to
          work.  Now you can only use letter characters for this purpose.  For example,
          <literal>to_timestamp('2000y6m1d', 'yyyytMMtDDt')</literal> and
          <literal>to_timestamp('2000y6m1d', 'yyyy"y"MM"m"DD"d"')</literal>
          skip <literal>y</literal>, <literal>m</literal>, and
          <literal>d</literal>.
        </para>
      </tip>
     </listitem>

     <listitem>
      <para>
       If you want to have a double quote in the output you must
       precede it with a backslash, for example <literal>'\"YYYY
       Month\"'</literal>. <!-- "" font-lock sanity :-) -->
       Backslashes are not otherwise special outside of double-quoted
       strings.  Within a double-quoted string, a backslash causes the
       next character to be taken literally, whatever it is (but this
       has no special effect unless the next character is a double quote
       or another backslash).
      </para>
     </listitem>

     <listitem>
      <para>
       In <function>to_timestamp</function> and <function>to_date</function>,
       if the year format specification is less than four digits, e.g.,
       <literal>YYY</literal>, and the supplied year is less than four digits,
       the year will be adjusted to be nearest to the year 2020, e.g.,
       <literal>95</literal> becomes 1995.
      </para>
     </listitem>

     <listitem>
      <para>
       In <function>to_timestamp</function> and <function>to_date</function>,
       negative years are treated as signifying BC.  If you write both a
       negative year and an explicit <literal>BC</literal> field, you get AD
       again.  An input of year zero is treated as 1 BC.
      </para>
     </listitem>

     <listitem>
      <para>
       In <function>to_timestamp</function> and <function>to_date</function>,
       the <literal>YYYY</literal> conversion has a restriction when
       processing years with more than 4 digits. You must
       use some non-digit character or template after <literal>YYYY</literal>,
       otherwise the year is always interpreted as 4 digits. For example
       (with the year 20000):
       <literal>to_date('200001130', 'YYYYMMDD')</literal> will be
       interpreted as a 4-digit year; instead use a non-digit
       separator after the year, like
       <literal>to_date('20000-1130', 'YYYY-MMDD')</literal> or
       <literal>to_date('20000Nov30', 'YYYYMonDD')</literal>.
      </para>
     </listitem>

     <listitem>
      <para>
       In <function>to_timestamp</function> and <function>to_date</function>,
       the <literal>CC</literal> (century) field is accepted but ignored
       if there is a <literal>YYY</literal>, <literal>YYYY</literal> or
       <literal>Y,YYY</literal> field. If <literal>CC</literal> is used with
       <literal>YY</literal> or <literal>Y</literal> then the result is
       computed as that year in the specified century.  If the century is
       specified but the year is not, the first year of the century
       is assumed.
      </para>
     </listitem>

     <listitem>
      <para>
       In <function>to_timestamp</function> and <function>to_date</function>,
       weekday names or numbers (<literal>DAY</literal>, <literal>D</literal>,
       and related field types) are accepted but are ignored for purposes of
       computing the result.  The same is true for quarter
       (<literal>Q</literal>) fields.
      </para>
     </listitem>

     <listitem>
      <para>
       In <function>to_timestamp</function> and <function>to_date</function>,
       an ISO 8601 week-numbering date (as distinct from a Gregorian date)
       can be specified in one of two ways:
       <itemizedlist>
        <listitem>
         <para>
          Year, week number, and weekday:  for
          example <literal>to_date('2006-42-4', 'IYYY-IW-ID')</literal>
          returns the date <literal>2006-10-19</literal>.
          If you omit the weekday it is assumed to be 1 (Monday).
         </para>
        </listitem>
        <listitem>
         <para>
          Year and day of year:  for example <literal>to_date('2006-291',
          'IYYY-IDDD')</literal> also returns <literal>2006-10-19</literal>.
         </para>
        </listitem>
       </itemizedlist>
      </para>
      <para>
       Attempting to enter a date using a mixture of ISO 8601 week-numbering
       fields and Gregorian date fields is nonsensical, and will cause an
       error.  In the context of an ISO 8601 week-numbering year, the
       concept of a <quote>month</quote> or <quote>day of month</quote> has no
       meaning.  In the context of a Gregorian year, the ISO week has no
       meaning.
      </para>
      <caution>
       <para>
        While <function>to_date</function> will reject a mixture of
        Gregorian and ISO week-numbering date
        fields, <function>to_char</function> will not, since output format
        specifications like <literal>YYYY-MM-DD (IYYY-IDDD)</literal> can be
        useful.  But avoid writing something like <literal>IYYY-MM-DD</literal>;
        that would yield surprising results near the start of the year.
        (See <xref linkend="functions-datetime-extract"/> for more
        information.)
       </para>
      </caution>
     </listitem>

     <listitem>
      <para>
       In <function>to_timestamp</function>, millisecond
       (<literal>MS</literal>) or microsecond (<literal>US</literal>)
       fields are used as the
       seconds digits after the decimal point. For example
       <literal>to_timestamp('12.3', 'SS.MS')</literal> is not 3 milliseconds,
       but 300, because the conversion treats it as 12 + 0.3 seconds.
       So, for the format <literal>SS.MS</literal>, the input values
       <literal>12.3</literal>, <literal>12.30</literal>,
       and <literal>12.300</literal> specify the
       same number of milliseconds. To get three milliseconds, one must write
       <literal>12.003</literal>, which the conversion treats as
       12 + 0.003 = 12.003 seconds.
      </para>

      <para>
       Here is a more
       complex example:
       <literal>to_timestamp('15:12:02.020.001230', 'HH24:MI:SS.MS.US')</literal>
       is 15 hours, 12 minutes, and 2 seconds + 20 milliseconds +
       1230 microseconds = 2.021230 seconds.
      </para>
     </listitem>

     <listitem>
      <para>
        <function>to_char(..., 'ID')</function>'s day of the week numbering
        matches the <function>extract(isodow FROM ...)</function> function, but
        <function>to_char(..., 'D')</function>'s does not match
        <function>extract(dow FROM ...)</function>'s day numbering.
      </para>
     </listitem>

     <listitem>
      <para>
        <function>to_char(interval)</function> formats <literal>HH</literal> and
        <literal>HH12</literal> as shown on a 12-hour clock, for example zero hours
        and 36 hours both output as <literal>12</literal>, while <literal>HH24</literal>
        outputs the full hour value, which can exceed 23 in
        an <type>interval</type> value.
      </para>
     </listitem>

    </itemizedlist>
   </para>

  <para>
   <xref linkend="functions-formatting-numeric-table"/> shows the
   template patterns available for formatting numeric values.
  </para>

    <table id="functions-formatting-numeric-table">
     <title>Template Patterns for Numeric Formatting</title>
     <tgroup cols="2">
      <colspec colname="col1" colwidth="1*"/>
      <colspec colname="col2" colwidth="3*"/>
      <thead>
       <row>
        <entry>Pattern</entry>
        <entry>Description</entry>
       </row>
      </thead>
      <tbody>
       <row>
        <entry><literal>9</literal></entry>
        <entry>digit position (can be dropped if insignificant)</entry>
       </row>
       <row>
        <entry><literal>0</literal></entry>
        <entry>digit position (will not be dropped, even if insignificant)</entry>
       </row>
       <row>
        <entry><literal>.</literal> (period)</entry>
        <entry>decimal point</entry>
       </row>
       <row>
        <entry><literal>,</literal> (comma)</entry>
        <entry>group (thousands) separator</entry>
       </row>
       <row>
        <entry><literal>PR</literal></entry>
        <entry>negative value in angle brackets</entry>
       </row>
       <row>
        <entry><literal>S</literal></entry>
        <entry>sign anchored to number (uses locale)</entry>
       </row>
       <row>
        <entry><literal>L</literal></entry>
        <entry>currency symbol (uses locale)</entry>
       </row>
       <row>
        <entry><literal>D</literal></entry>
        <entry>decimal point (uses locale)</entry>
       </row>
       <row>
        <entry><literal>G</literal></entry>
        <entry>group separator (uses locale)</entry>
       </row>
       <row>
        <entry><literal>MI</literal></entry>
        <entry>minus sign in specified position (if number &lt; 0)</entry>
       </row>
       <row>
        <entry><literal>PL</literal></entry>
        <entry>plus sign in specified position (if number &gt; 0)</entry>
       </row>
       <row>
        <entry><literal>SG</literal></entry>
        <entry>plus/minus sign in specified position</entry>
       </row>
       <row>
        <entry><literal>RN</literal> or <literal>rn</literal></entry>
        <entry>Roman numeral (values between 1 and 3999)</entry>
       </row>
       <row>
        <entry><literal>TH</literal> or <literal>th</literal></entry>
        <entry>ordinal number suffix</entry>
       </row>
       <row>
        <entry><literal>V</literal></entry>
        <entry>shift specified number of digits (see notes)</entry>
       </row>
       <row>
        <entry><literal>EEEE</literal></entry>
        <entry>exponent for scientific notation</entry>
       </row>
      </tbody>
     </tgroup>
    </table>

   <para>
    Usage notes for numeric formatting:

    <itemizedlist>
     <listitem>
      <para>
       <literal>0</literal> specifies a digit position that will always be printed,
       even if it contains a leading/trailing zero.  <literal>9</literal> also
       specifies a digit position, but if it is a leading zero then it will
       be replaced by a space, while if it is a trailing zero and fill mode
       is specified then it will be deleted.  (For <function>to_number()</function>,
       these two pattern characters are equivalent.)
      </para>
     </listitem>

     <listitem>
      <para>
       If the format provides fewer fractional digits than the number being
       formatted, <function>to_char()</function> will round the number to
       the specified number of fractional digits.
      </para>
     </listitem>

     <listitem>
      <para>
       The pattern characters <literal>S</literal>, <literal>L</literal>, <literal>D</literal>,
       and <literal>G</literal> represent the sign, currency symbol, decimal point,
       and thousands separator characters defined by the current locale
       (see <xref linkend="guc-lc-monetary"/>
       and <xref linkend="guc-lc-numeric"/>).  The pattern characters period
       and comma represent those exact characters, with the meanings of
       decimal point and thousands separator, regardless of locale.
      </para>
     </listitem>

     <listitem>
      <para>
       If no explicit provision is made for a sign
       in <function>to_char()</function>'s pattern, one column will be reserved for
       the sign, and it will be anchored to (appear just left of) the
       number.  If <literal>S</literal> appears just left of some <literal>9</literal>'s,
       it will likewise be anchored to the number.
      </para>
     </listitem>

     <listitem>
      <para>
       A sign formatted using <literal>SG</literal>, <literal>PL</literal>, or
       <literal>MI</literal> is not anchored to
       the number; for example,
       <literal>to_char(-12, 'MI9999')</literal> produces <literal>'-&nbsp;&nbsp;12'</literal>
       but <literal>to_char(-12, 'S9999')</literal> produces <literal>'&nbsp;&nbsp;-12'</literal>.
       (The Oracle implementation does not allow the use of
       <literal>MI</literal> before <literal>9</literal>, but rather
       requires that <literal>9</literal> precede
       <literal>MI</literal>.)
      </para>
     </listitem>

     <listitem>
      <para>
       <literal>TH</literal> does not convert values less than zero
       and does not convert fractional numbers.
      </para>
     </listitem>

     <listitem>
      <para>
       <literal>PL</literal>, <literal>SG</literal>, and
       <literal>TH</literal> are <productname>PostgreSQL</productname>
       extensions.
      </para>
     </listitem>

     <listitem>
      <para>
       In <function>to_number</function>, if non-data template patterns such
       as <literal>L</literal> or <literal>TH</literal> are used, the
       corresponding number of input characters are skipped, whether or not
       they match the template pattern, unless they are data characters
       (that is, digits, sign, decimal point, or comma).  For
       example, <literal>TH</literal> would skip two non-data characters.
      </para>
     </listitem>

     <listitem>
      <para>
       <literal>V</literal> with <function>to_char</function>
       multiplies the input values by
       <literal>10^<replaceable>n</replaceable></literal>, where
       <replaceable>n</replaceable> is the number of digits following
       <literal>V</literal>.  <literal>V</literal> with
       <function>to_number</function> divides in a similar manner.
       The <literal>V</literal> can be thought of as marking the position
       of an implicit decimal point in the input or output string.
       <function>to_char</function> and <function>to_number</function>
       do not support the use of
       <literal>V</literal> combined with a decimal point
       (e.g., <literal>99.9V99</literal> is not allowed).
      </para>
     </listitem>

     <listitem>
      <para>
       <literal>EEEE</literal> (scientific notation) cannot be used in
       combination with any of the other formatting patterns or
       modifiers other than digit and decimal point patterns, and must be at the end of the format string
       (e.g., <literal>9.99EEEE</literal> is a valid pattern).
      </para>
     </listitem>

     <listitem>
      <para>
       In <function>to_number()</function>, the <literal>RN</literal>
       pattern converts Roman numerals (in standard form) to numbers.
       Input is case-insensitive, so <literal>RN</literal>
       and <literal>rn</literal> are equivalent.  <literal>RN</literal>
       cannot be used in combination with any other formatting patterns or
       modifiers except <literal>FM</literal>, which is applicable only
       in <function>to_char()</function> and is ignored
       in <function>to_number()</function>.
      </para>
     </listitem>
    </itemizedlist>
   </para>

   <para>
    Certain modifiers can be applied to any template pattern to alter its
    behavior.  For example, <literal>FM99.99</literal>
    is the <literal>99.99</literal> pattern with the
    <literal>FM</literal> modifier.
    <xref linkend="functions-formatting-numericmod-table"/> shows the
    modifier patterns for numeric formatting.
   </para>

    <table id="functions-formatting-numericmod-table">
     <title>Template Pattern Modifiers for Numeric Formatting</title>
     <tgroup cols="3">
      <thead>
       <row>
        <entry>Modifier</entry>
        <entry>Description</entry>
        <entry>Example</entry>
       </row>
      </thead>
      <tbody>
       <row>
        <entry><literal>FM</literal> prefix</entry>
        <entry>fill mode (suppress trailing zeroes and padding blanks)</entry>
        <entry><literal>FM99.99</literal></entry>
       </row>
       <row>
        <entry><literal>TH</literal> suffix</entry>
        <entry>upper case ordinal number suffix</entry>
        <entry><literal>999TH</literal></entry>
       </row>
       <row>
        <entry><literal>th</literal> suffix</entry>
        <entry>lower case ordinal number suffix</entry>
        <entry><literal>999th</literal></entry>
       </row>
      </tbody>
     </tgroup>
    </table>

  <para>
   <xref linkend="functions-formatting-examples-table"/> shows some
   examples of the use of the <function>to_char</function> function.
  </para>

    <table id="functions-formatting-examples-table">
     <title><function>to_char</function> Examples</title>
     <tgroup cols="2">
      <thead>
       <row>
        <entry>Expression</entry>
        <entry>Result</entry>
       </row>
      </thead>
      <tbody>
       <row>
        <entry><literal>to_char(current_timestamp, 'Day,&nbsp;DD&nbsp;&nbsp;HH12:MI:SS')</literal></entry>
        <entry><literal>'Tuesday&nbsp;&nbsp;,&nbsp;06&nbsp;&nbsp;05:39:18'</literal></entry>
       </row>
       <row>
        <entry><literal>to_char(current_timestamp, 'FMDay,&nbsp;FMDD&nbsp;&nbsp;HH12:MI:SS')</literal></entry>
        <entry><literal>'Tuesday,&nbsp;6&nbsp;&nbsp;05:39:18'</literal></entry>
       </row>
       <row>
        <entry><literal>to_char(current_timestamp AT TIME ZONE
        'UTC', 'YYYY-MM-DD"T"HH24:MI:SS"Z"')</literal></entry>
        <entry><literal>'2022-12-06T05:39:18Z'</literal>,
        <acronym>ISO</acronym> 8601 extended format</entry>
       </row>
       <row>
        <entry><literal>to_char(-0.1, '99.99')</literal></entry>
        <entry><literal>'&nbsp;&nbsp;-.10'</literal></entry>
       </row>
       <row>
        <entry><literal>to_char(-0.1, 'FM9.99')</literal></entry>
        <entry><literal>'-.1'</literal></entry>
       </row>
       <row>
        <entry><literal>to_char(-0.1, 'FM90.99')</literal></entry>
        <entry><literal>'-0.1'</literal></entry>
       </row>
       <row>
        <entry><literal>to_char(0.1, '0.9')</literal></entry>
        <entry><literal>'&nbsp;0.1'</literal></entry>
       </row>
       <row>
        <entry><literal>to_char(12, '9990999.9')</literal></entry>
        <entry><literal>'&nbsp;&nbsp;&nbsp;&nbsp;0012.0'</literal></entry>
       </row>
       <row>
        <entry><literal>to_char(12, 'FM9990999.9')</literal></entry>
        <entry><literal>'0012.'</literal></entry>
       </row>
       <row>
        <entry><literal>to_char(485, '999')</literal></entry>
        <entry><literal>'&nbsp;485'</literal></entry>
       </row>
       <row>
        <entry><literal>to_char(-485, '999')</literal></entry>
        <entry><literal>'-485'</literal></entry>
       </row>
       <row>
        <entry><literal>to_char(485, '9&nbsp;9&nbsp;9')</literal></entry>
        <entry><literal>'&nbsp;4&nbsp;8&nbsp;5'</literal></entry>
       </row>
       <row>
        <entry><literal>to_char(1485, '9,999')</literal></entry>
        <entry><literal>'&nbsp;1,485'</literal></entry>
       </row>
       <row>
        <entry><literal>to_char(1485, '9G999')</literal></entry>
        <entry><literal>'&nbsp;1&nbsp;485'</literal></entry>
       </row>
       <row>
        <entry><literal>to_char(148.5, '999.999')</literal></entry>
        <entry><literal>'&nbsp;148.500'</literal></entry>
       </row>
       <row>
        <entry><literal>to_char(148.5, 'FM999.999')</literal></entry>
        <entry><literal>'148.5'</literal></entry>
       </row>
       <row>
        <entry><literal>to_char(148.5, 'FM999.990')</literal></entry>
        <entry><literal>'148.500'</literal></entry>
       </row>
       <row>
        <entry><literal>to_char(148.5, '999D999')</literal></entry>
        <entry><literal>'&nbsp;148,500'</literal></entry>
       </row>
       <row>
        <entry><literal>to_char(3148.5, '9G999D999')</literal></entry>
        <entry><literal>'&nbsp;3&nbsp;148,500'</literal></entry>
       </row>
       <row>
        <entry><literal>to_char(-485, '999S')</literal></entry>
        <entry><literal>'485-'</literal></entry>
       </row>
       <row>
        <entry><literal>to_char(-485, '999MI')</literal></entry>
        <entry><literal>'485-'</literal></entry>
       </row>
       <row>
        <entry><literal>to_char(485, '999MI')</literal></entry>
        <entry><literal>'485&nbsp;'</literal></entry>
       </row>
       <row>
        <entry><literal>to_char(485, 'FM999MI')</literal></entry>
        <entry><literal>'485'</literal></entry>
       </row>
       <row>
        <entry><literal>to_char(485, 'PL999')</literal></entry>
        <entry><literal>'+485'</literal></entry>
       </row>
       <row>
        <entry><literal>to_char(485, 'SG999')</literal></entry>
        <entry><literal>'+485'</literal></entry>
       </row>
       <row>
        <entry><literal>to_char(-485, 'SG999')</literal></entry>
        <entry><literal>'-485'</literal></entry>
       </row>
       <row>
        <entry><literal>to_char(-485, '9SG99')</literal></entry>
        <entry><literal>'4-85'</literal></entry>
       </row>
       <row>
        <entry><literal>to_char(-485, '999PR')</literal></entry>
        <entry><literal>'&lt;485&gt;'</literal></entry>
       </row>
       <row>
        <entry><literal>to_char(485, 'L999')</literal></entry>
        <entry><literal>'DM&nbsp;485'</literal></entry>
       </row>
       <row>
        <entry><literal>to_char(485, 'RN')</literal></entry>
        <entry><literal>'&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;CDLXXXV'</literal></entry>
       </row>
       <row>
        <entry><literal>to_char(485, 'FMRN')</literal></entry>
        <entry><literal>'CDLXXXV'</literal></entry>
       </row>
       <row>
        <entry><literal>to_char(5.2, 'FMRN')</literal></entry>
        <entry><literal>'V'</literal></entry>
       </row>
       <row>
        <entry><literal>to_char(482, '999th')</literal></entry>
        <entry><literal>'&nbsp;482nd'</literal></entry>
       </row>
       <row>
        <entry><literal>to_char(485, '"Good&nbsp;number:"999')</literal></entry>
        <entry><literal>'Good&nbsp;number:&nbsp;485'</literal></entry>
       </row>
       <row>
        <entry><literal>to_char(485.8, '"Pre:"999"&nbsp;Post:"&nbsp;.999')</literal></entry>
        <entry><literal>'Pre:&nbsp;485&nbsp;Post:&nbsp;.800'</literal></entry>
       </row>
       <row>
        <entry><literal>to_char(12, '99V999')</literal></entry>
        <entry><literal>'&nbsp;12000'</literal></entry>
       </row>
       <row>
        <entry><literal>to_char(12.4, '99V999')</literal></entry>
        <entry><literal>'&nbsp;12400'</literal></entry>
       </row>
       <row>
        <entry><literal>to_char(12.45, '99V9')</literal></entry>
        <entry><literal>'&nbsp;125'</literal></entry>
       </row>
       <row>
        <entry><literal>to_char(0.0004859, '9.99EEEE')</literal></entry>
        <entry><literal>' 4.86e-04'</literal></entry>
       </row>
      </tbody>
     </tgroup>
    </table>

  </sect1>