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9.8. Data Type Formatting Functions #

   The PostgreSQL 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. Table 9.26 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.

   Table 9.26. Formatting Functions

   Function

   Description

   Example(s)

   to_char ( timestamp, text ) → text

   to_char ( timestamp with time zone, text ) → text

   Converts time stamp to string according to the given format.

   to_char(timestamp '2002-04-20 17:31:12.66', 'HH12:MI:SS') → 05:31:12

   to_char ( interval, text ) → text

   Converts interval to string according to the given format.

   to_char(interval '15h 2m 12s', 'HH24:MI:SS') → 15:02:12

   to_char ( numeric_type, text ) → text

   Converts number to string according to the given format; available for
   integer, bigint, numeric, real, double precision.

   to_char(125, '999') → 125

   to_char(125.8::real, '999D9') → 125.8

   to_char(-125.8, '999D99S') → 125.80-

   to_date ( text, text ) → date

   Converts string to date according to the given format.

   to_date('05 Dec 2000', 'DD Mon YYYY') → 2000-12-05

   to_number ( text, text ) → numeric

   Converts string to numeric according to the given format.

   to_number('12,454.8-', '99G999D9S') → -12454.8

   to_timestamp ( text, text ) → timestamp with time zone

   Converts string to time stamp according to the given format. (See also
   to_timestamp(double precision) in Table 9.33.)

   to_timestamp('05 Dec 2000', 'DD Mon YYYY') → 2000-12-05 00:00:00-05

Tip

   to_timestamp and to_date 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, to_number is unnecessary for standard
   numeric representations.

   In a to_char 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).

   Table 9.27 shows the template patterns available for formatting date
   and time values.

   Table 9.27. Template Patterns for Date/Time Formatting
   Pattern Description
   HH hour of day (01–12)
   HH12 hour of day (01–12)
   HH24 hour of day (00–23)
   MI minute (00–59)
   SS second (00–59)
   MS millisecond (000–999)
   US microsecond (000000–999999)
   FF1 tenth of second (0–9)
   FF2 hundredth of second (00–99)
   FF3 millisecond (000–999)
   FF4 tenth of a millisecond (0000–9999)
   FF5 hundredth of a millisecond (00000–99999)
   FF6 microsecond (000000–999999)
   SSSS, SSSSS seconds past midnight (0–86399)
   AM, am, PM or pm meridiem indicator (without periods)
   A.M., a.m., P.M. or p.m. meridiem indicator (with periods)
   Y,YYY year (4 or more digits) with comma
   YYYY year (4 or more digits)
   YYY last 3 digits of year
   YY last 2 digits of year
   Y last digit of year
   IYYY ISO 8601 week-numbering year (4 or more digits)
   IYY last 3 digits of ISO 8601 week-numbering year
   IY last 2 digits of ISO 8601 week-numbering year
   I last digit of ISO 8601 week-numbering year
   BC, bc, AD or ad era indicator (without periods)
   B.C., b.c., A.D. or a.d. era indicator (with periods)
   MONTH full upper case month name (blank-padded to 9 chars)
   Month full capitalized month name (blank-padded to 9 chars)
   month full lower case month name (blank-padded to 9 chars)
   MON abbreviated upper case month name (3 chars in English, localized
   lengths vary)
   Mon abbreviated capitalized month name (3 chars in English, localized
   lengths vary)
   mon abbreviated lower case month name (3 chars in English, localized
   lengths vary)
   MM month number (01–12)
   DAY full upper case day name (blank-padded to 9 chars)
   Day full capitalized day name (blank-padded to 9 chars)
   day full lower case day name (blank-padded to 9 chars)
   DY abbreviated upper case day name (3 chars in English, localized
   lengths vary)
   Dy abbreviated capitalized day name (3 chars in English, localized
   lengths vary)
   dy abbreviated lower case day name (3 chars in English, localized
   lengths vary)
   DDD day of year (001–366)
   IDDD day of ISO 8601 week-numbering year (001–371; day 1 of the year is
   Monday of the first ISO week)
   DD day of month (01–31)
   D day of the week, Sunday (1) to Saturday (7)
   ID ISO 8601 day of the week, Monday (1) to Sunday (7)
   W week of month (1–5) (the first week starts on the first day of the
   month)
   WW week number of year (1–53) (the first week starts on the first day
   of the year)
   IW week number of ISO 8601 week-numbering year (01–53; the first
   Thursday of the year is in week 1)
   CC century (2 digits) (the twenty-first century starts on 2001-01-01)
   J Julian Date (integer days since November 24, 4714 BC at local
   midnight; see Section B.7)
   Q quarter
   RM month in upper case Roman numerals (I–XII; I=January)
   rm month in lower case Roman numerals (i–xii; i=January)
   TZ upper case time-zone abbreviation
   tz lower case time-zone abbreviation
   TZH time-zone hours
   TZM time-zone minutes
   OF time-zone offset from UTC (HH or HH:MM)

   Modifiers can be applied to any template pattern to alter its behavior.
   For example, FMMonth is the Month pattern with the FM modifier.
   Table 9.28 shows the modifier patterns for date/time formatting.

   Table 9.28. Template Pattern Modifiers for Date/Time Formatting
   Modifier Description Example
   FM prefix fill mode (suppress leading zeroes and padding blanks)
   FMMonth
   TH suffix upper case ordinal number suffix DDTH, e.g., 12TH
   th suffix lower case ordinal number suffix DDth, e.g., 12th
   FX prefix fixed format global option (see usage notes) FX Month DD Day
   TM prefix translation mode (use localized day and month names based on
   lc_time) TMMonth
   SP suffix spell mode (not implemented) DDSP

   Usage notes for date/time formatting:
     * FM suppresses leading zeroes and trailing blanks that would
       otherwise be added to make the output of a pattern be fixed-width.
       In PostgreSQL, FM modifies only the next specification, while in
       Oracle FM affects all subsequent specifications, and repeated FM
       modifiers toggle fill mode on and off.
     * TM suppresses trailing blanks whether or not FM is specified.
     * to_timestamp and to_date ignore letter case in the input; so for
       example MON, Mon, and mon all accept the same strings. When using
       the TM modifier, case-folding is done according to the rules of the
       function's input collation (see Section 23.2).
     * to_timestamp and to_date skip multiple blank spaces at the
       beginning of the input string and around date and time values
       unless the FX option is used. For example,
       to_timestamp(' 2000    JUN', 'YYYY MON') and to_timestamp('2000 -
       JUN', 'YYYY-MON') work, but to_timestamp('2000    JUN', 'FXYYYY
       MON') returns an error because to_timestamp expects only a single
       space. FX must be specified as the first item in the template.
     * A separator (a space or non-letter/non-digit character) in the
       template string of to_timestamp and to_date matches any single
       separator in the input string or is skipped, unless the FX option
       is used. For example, to_timestamp('2000JUN', 'YYYY///MON') and
       to_timestamp('2000/JUN', 'YYYY MON') work, but
       to_timestamp('2000//JUN', 'YYYY/MON') returns an error because the
       number of separators in the input string exceeds the number of
       separators in the template.
       If FX 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, to_timestamp('2000/JUN',
       'FXYYYY MON') works, but to_timestamp('2000/JUN', 'FXYYYY  MON')
       returns an error because the second space in the template string
       consumes the letter J from the input string.
     * A TZH template pattern can match a signed number. Without the FX
       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 TZH 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 TZH. Otherwise, the minus sign
       is considered to be a separator between values. For example,
       to_timestamp('2000 -10', 'YYYY TZH') matches -10 to TZH, but
       to_timestamp('2000 -10', 'YYYY  TZH') matches 10 to TZH.
     * Ordinary text is allowed in to_char 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 '"Hello Year "YYYY', the YYYY will be
       replaced by the year data, but the single Y in Year will not be. In
       to_date, to_number, and to_timestamp, literal text and
       double-quoted strings result in skipping the number of characters
       contained in the string; for example "XX" skips two input
       characters (whether or not they are XX).

Tip
       Prior to PostgreSQL 12, it was possible to skip arbitrary text in
       the input string using non-letter or non-digit characters. For
       example, to_timestamp('2000y6m1d', 'yyyy-MM-DD') used to work. Now
       you can only use letter characters for this purpose. For example,
       to_timestamp('2000y6m1d', 'yyyytMMtDDt') and
       to_timestamp('2000y6m1d', 'yyyy"y"MM"m"DD"d"') skip y, m, and d.
     * If you want to have a double quote in the output you must precede
       it with a backslash, for example '\"YYYY Month\"'. 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).
     * In to_timestamp and to_date, if the year format specification is
       less than four digits, e.g., YYY, and the supplied year is less
       than four digits, the year will be adjusted to be nearest to the
       year 2020, e.g., 95 becomes 1995.
     * In to_timestamp and to_date, negative years are treated as
       signifying BC. If you write both a negative year and an explicit BC
       field, you get AD again. An input of year zero is treated as 1 BC.
     * In to_timestamp and to_date, the YYYY conversion has a restriction
       when processing years with more than 4 digits. You must use some
       non-digit character or template after YYYY, otherwise the year is
       always interpreted as 4 digits. For example (with the year 20000):
       to_date('200001130', 'YYYYMMDD') will be interpreted as a 4-digit
       year; instead use a non-digit separator after the year, like
       to_date('20000-1130', 'YYYY-MMDD') or to_date('20000Nov30',
       'YYYYMonDD').
     * In to_timestamp and to_date, the CC (century) field is accepted but
       ignored if there is a YYY, YYYY or Y,YYY field. If CC is used with
       YY or Y 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.
     * In to_timestamp and to_date, weekday names or numbers (DAY, D, and
       related field types) are accepted but are ignored for purposes of
       computing the result. The same is true for quarter (Q) fields.
     * In to_timestamp and to_date, an ISO 8601 week-numbering date (as
       distinct from a Gregorian date) can be specified in one of two
       ways:
          + Year, week number, and weekday: for example
            to_date('2006-42-4', 'IYYY-IW-ID') returns the date
            2006-10-19. If you omit the weekday it is assumed to be 1
            (Monday).
          + Year and day of year: for example to_date('2006-291',
            'IYYY-IDDD') also returns 2006-10-19.
       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 “month” or “day of month” has no meaning. In
       the context of a Gregorian year, the ISO week has no meaning.

Caution
       While to_date will reject a mixture of Gregorian and ISO
       week-numbering date fields, to_char will not, since output format
       specifications like YYYY-MM-DD (IYYY-IDDD) can be useful. But avoid
       writing something like IYYY-MM-DD; that would yield surprising
       results near the start of the year. (See Section 9.9.1 for more
       information.)
     * In to_timestamp, millisecond (MS) or microsecond (US) fields are
       used as the seconds digits after the decimal point. For example
       to_timestamp('12.3', 'SS.MS') is not 3 milliseconds, but 300,
       because the conversion treats it as 12 + 0.3 seconds. So, for the
       format SS.MS, the input values 12.3, 12.30, and 12.300 specify the
       same number of milliseconds. To get three milliseconds, one must
       write 12.003, which the conversion treats as 12 + 0.003 = 12.003
       seconds.
       Here is a more complex example: to_timestamp('15:12:02.020.001230',
       'HH24:MI:SS.MS.US') is 15 hours, 12 minutes, and 2 seconds + 20
       milliseconds + 1230 microseconds = 2.021230 seconds.
     * to_char(..., 'ID')'s day of the week numbering matches the
       extract(isodow from ...) function, but to_char(..., 'D')'s does not
       match extract(dow from ...)'s day numbering.
     * to_char(interval) formats HH and HH12 as shown on a 12-hour clock,
       for example zero hours and 36 hours both output as 12, while HH24
       outputs the full hour value, which can exceed 23 in an interval
       value.

   Table 9.29 shows the template patterns available for formatting numeric
   values.

   Table 9.29. Template Patterns for Numeric Formatting
    Pattern                           Description
   9          digit position (can be dropped if insignificant)
   0          digit position (will not be dropped, even if insignificant)
   . (period) decimal point
   , (comma)  group (thousands) separator
   PR         negative value in angle brackets
   S          sign anchored to number (uses locale)
   L          currency symbol (uses locale)
   D          decimal point (uses locale)
   G          group separator (uses locale)
   MI         minus sign in specified position (if number < 0)
   PL         plus sign in specified position (if number > 0)
   SG         plus/minus sign in specified position
   RN or rn   Roman numeral (values between 1 and 3999)
   TH or th   ordinal number suffix
   V          shift specified number of digits (see notes)
   EEEE       exponent for scientific notation

   Usage notes for numeric formatting:
     * 0 specifies a digit position that will always be printed, even if
       it contains a leading/trailing zero. 9 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 to_number(), these two pattern
       characters are equivalent.)
     * If the format provides fewer fractional digits than the number
       being formatted, to_char() will round the number to the specified
       number of fractional digits.
     * The pattern characters S, L, D, and G represent the sign, currency
       symbol, decimal point, and thousands separator characters defined
       by the current locale (see lc_monetary and lc_numeric). The pattern
       characters period and comma represent those exact characters, with
       the meanings of decimal point and thousands separator, regardless
       of locale.
     * If no explicit provision is made for a sign in to_char()'s pattern,
       one column will be reserved for the sign, and it will be anchored
       to (appear just left of) the number. If S appears just left of some
       9's, it will likewise be anchored to the number.
     * A sign formatted using SG, PL, or MI is not anchored to the number;
       for example, to_char(-12, 'MI9999') produces '-  12' but
       to_char(-12, 'S9999') produces '  -12'. (The Oracle implementation
       does not allow the use of MI before 9, but rather requires that 9
       precede MI.)
     * TH does not convert values less than zero and does not convert
       fractional numbers.
     * PL, SG, and TH are PostgreSQL extensions.
     * In to_number, if non-data template patterns such as L or TH 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, TH would skip two non-data characters.
     * V with to_char multiplies the input values by 10^n, where n is the
       number of digits following V. V with to_number divides in a similar
       manner. The V can be thought of as marking the position of an
       implicit decimal point in the input or output string. to_char and
       to_number do not support the use of V combined with a decimal point
       (e.g., 99.9V99 is not allowed).
     * EEEE (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., 9.99EEEE is a valid pattern).
     * In to_number(), the RN pattern converts Roman numerals (in standard
       form) to numbers. Input is case-insensitive, so RN and rn are
       equivalent. RN cannot be used in combination with any other
       formatting patterns or modifiers except FM, which is applicable
       only in to_char() and is ignored in to_number().

   Certain modifiers can be applied to any template pattern to alter its
   behavior. For example, FM99.99 is the 99.99 pattern with the FM
   modifier. Table 9.30 shows the modifier patterns for numeric
   formatting.

   Table 9.30. Template Pattern Modifiers for Numeric Formatting
   Modifier                        Description                       Example
   FM prefix fill mode (suppress trailing zeroes and padding blanks)
   FM99.99
   TH suffix upper case ordinal number suffix                        999TH
   th suffix lower case ordinal number suffix                        999th

   Table 9.31 shows some examples of the use of the to_char function.

   Table 9.31. to_char Examples
   Expression Result
   to_char(current_timestamp, 'Day, DD  HH12:MI:SS')
   'Tuesday  , 06  05:39:18'
   to_char(current_timestamp, 'FMDay, FMDD  HH12:MI:SS')
   'Tuesday, 6  05:39:18'
   to_char(current_timestamp AT TIME ZONE 'UTC',
   'YYYY-MM-DD"T"HH24:MI:SS"Z"') '2022-12-06T05:39:18Z', ISO 8601 extended
   format
   to_char(-0.1, '99.99') '  -.10'
   to_char(-0.1, 'FM9.99') '-.1'
   to_char(-0.1, 'FM90.99') '-0.1'
   to_char(0.1, '0.9') ' 0.1'
   to_char(12, '9990999.9') '    0012.0'
   to_char(12, 'FM9990999.9') '0012.'
   to_char(485, '999') ' 485'
   to_char(-485, '999') '-485'
   to_char(485, '9 9 9') ' 4 8 5'
   to_char(1485, '9,999') ' 1,485'
   to_char(1485, '9G999') ' 1 485'
   to_char(148.5, '999.999') ' 148.500'
   to_char(148.5, 'FM999.999') '148.5'
   to_char(148.5, 'FM999.990') '148.500'
   to_char(148.5, '999D999') ' 148,500'
   to_char(3148.5, '9G999D999') ' 3 148,500'
   to_char(-485, '999S') '485-'
   to_char(-485, '999MI') '485-'
   to_char(485, '999MI') '485 '
   to_char(485, 'FM999MI') '485'
   to_char(485, 'PL999') '+485'
   to_char(485, 'SG999') '+485'
   to_char(-485, 'SG999') '-485'
   to_char(-485, '9SG99') '4-85'
   to_char(-485, '999PR') '<485>'
   to_char(485, 'L999') 'DM 485'
   to_char(485, 'RN') '        CDLXXXV'
   to_char(485, 'FMRN') 'CDLXXXV'
   to_char(5.2, 'FMRN') 'V'
   to_char(482, '999th') ' 482nd'
   to_char(485, '"Good number:"999') 'Good number: 485'
   to_char(485.8, '"Pre:"999" Post:" .999') 'Pre: 485 Post: .800'
   to_char(12, '99V999') ' 12000'
   to_char(12.4, '99V999') ' 12400'
   to_char(12.45, '99V9') ' 125'
   to_char(0.0004859, '9.99EEEE') ' 4.86e-04'