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4.6. Formatting Functions

Author: Written by Karel Zak () on 2000-01-24

The Postgres 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. 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 4-9. Formatting Functions

Function Returns Description Example
to_char(timestamp, text) text convert timestamp to string to_char(timestamp 'now','HH12:MI:SS')
to_char(int, text) text convert int4/int8 to string to_char(125, '999')
to_char(double precision, text) text convert real/double precision to string to_char(125.8, '999D9')
to_char(numeric, text) text convert numeric to string to_char(numeric '-125.8', '999D99S')
to_date(text, text) date convert string to date to_date('05 Dec 2000', 'DD Mon YYYY')
to_timestamp(text, text) timestamp convert string to timestamp to_timestamp('05 Dec 2000', 'DD Mon YYYY')
to_number(text, text) numeric convert string to numeric to_number('12,454.8-', '99G999D9S')

In an output template string, there are certain patterns that are recognized and replaced with appropriately-formatted data from the value to be formatted. Any text that is not a template pattern is simply copied verbatim. Similarly, in an input template string template patterns identify the parts of the input data string to be looked at and the values to be found there.

Table 4-10. Template patterns for date/time conversions

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)
SSSS seconds past midnight (0-86399)
AM or A.M. or PM or P.M. meridian indicator (upper case)
am or a.m. or pm or p.m. meridian indicator (lower case)
Y,YYY year (4 and more digits) with comma
YYYY year (4 and more digits)
YYY last 3 digits of year
YY last 2 digits of year
Y last digit of year
BC or B.C. or AD or A.D. year indicator (upper case)
bc or b.c. or ad or a.d. year indicator (lower case)
MONTH full upper case month name (blank-padded to 9 chars)
Month full mixed case 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)
Mon abbreviated mixed case month name (3 chars)
mon abbreviated lower case month name (3 chars)
MM month number (01-12)
DAY full upper case day name (blank-padded to 9 chars)
Day full mixed case 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)
Dy abbreviated mixed case day name (3 chars)
dy abbreviated lower case day name (3 chars)
DDD day of year (001-366)
DD day of month (01-31)
D day of week (1-7; SUN=1)
W week of month (1-5) where first week start on the first day of the month
WW week number of year (1-53) where first week start on the first day of the year
IW ISO week number of year (The first Thursday of the new year is in week 1.)
CC century (2 digits)
J Julian Day (days since January 1, 4712 BC)
Q quarter
RM month in Roman Numerals (I-XII; I=January) - upper case
rm month in Roman Numerals (I-XII; I=January) - lower case
TZ timezone name - upper case
tz timezone name - lower case

Certain modifiers may be applied to any template pattern to alter its behavior. For example, "FMMonth" is the "Month" pattern with the "FM" prefix.

Table 4-11. Template pattern modifiers for date/time conversions

Modifier Description Example
FM prefix fill mode (suppress padding blanks and zeroes) FMMonth
TH suffix add upper-case ordinal number suffix DDTH
th suffix add lower-case ordinal number suffix DDth
FX prefix FiXed format global option (see below) FX Month DD Day
SP suffix spell mode (not yet implemented) DDSP

Usage notes:

  • FM suppresses leading zeroes or trailing blanks that would otherwise be added to make the output of a pattern be fixed-width.

  • to_timestamp and to_date skip multiple blank spaces in the input string if the FX option is not used. FX must be specified as the first item in the template; for example to_timestamp('2000 JUN','YYYY MON') is right, but to_timestamp('2000 JUN','FXYYYY MON') returns an error, because to_timestamp expects one blank space only.

  • If a backslash ("\") is desired in a string constant, a double backslash ("\\") must be entered; for example '\\HH\\MI\\SS'. This is true for any string constant in Postgres.

  • 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 pattern keywords. For example, in '"Hello Year: "YYYY', the YYYY will be replaced by year data, but the single Y will not be.

  • If you want to have a double quote in the output you must precede it with a backslash, for example '\\"YYYY Month\\"'.

  • YYYY conversion from string to timestamp or date is restricted if you use a year 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 year 20000): to_date('200001131', 'YYYYMMDD') will be interpreted as a 4-digit year; better is to use a non-digit separator after the year, like to_date('20000-1131', 'YYYY-MMDD') or to_date('20000Nov31', 'YYYYMonDD').

Table 4-12. Template patterns for numeric conversions

Pattern Description
9 value with the specified number of digits
0 value with leading zeros
. (period) decimal point
, (comma) group (thousand) separator
PR negative value in angle brackets
S negative value with minus sign (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 roman numeral (input between 1 and 3999)
TH or th convert to ordinal number
V shift n digits (see notes)
EEEE scientific numbers (not supported yet)

Usage notes:

  • A sign formatted using 'SG', 'PL' or 'MI' is not an anchor in the number; for example, to_char(-12, 'S9999') produces ' -12', but to_char(-12, 'MI9999') produces '- 12'. The Oracle implementation does not allow the use of MI ahead of 9, but rather requires that 9 precede MI.

  • 9 specifies a value with the same number of digits as there are 9s. If a digit is not available use blank space.

  • TH does not convert values less than zero and does not convert decimal numbers.

  • PL, SG, and TH are Postgres extensions.

  • V effectively multiplies the input values by 10^n, where n is the number of digits following V. to_char does not support the use of V combined with a decimal point. (E.g., 99.9V99 is not allowed.)

Table 4-13. to_char Examples

Input Output
to_char(now(),'Day, DD HH12:MI:SS') 'Tuesday , 06 05:39:18'
to_char(now(),'FMDay, FMDD HH12:MI:SS') 'Tuesday, 6 05:39:18'
to_char(-0.1,'99.99') ' -.10'
to_char(-0.1,'FM9.99') '-.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,'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,'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'
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