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The PostgreSQL 9.0 Reference Manual - Volume 1A - SQL Language Reference
by The PostgreSQL Global Development Group
Paperback (6"x9"), 454 pages
ISBN 9781906966041
RRP £14.95 ($19.95)

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7.8 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 7-20 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.

A single-argument to_timestamp function is also available; it accepts a double precision argument and converts from Unix epoch (seconds since 1970-01-01 00:00:00+00) to timestamp with time zone. (Integer Unix epochs are implicitly cast to double precision.)

Table 7-20: Formatting Functions
Function Return Type Description
to_char(timestamp, text) text convert time stamp to string
e.g. to_char(current_timestamp, 'HH12:MI:SS')
to_char(interval, text) text convert interval to string
e.g. to_char(interval '15h 2m 12s', 'HH24:MI:SS')
to_char(int, text) text convert integer to string
e.g. to_char(125, '999')
to_char(double precision, text) text convert real/double precision to string
e.g. to_char(125.8::real, '999D9')
to_char(numeric, text) text convert numeric to string
e.g. to_char(-125.8, '999D99S')
to_date(text, text) date convert string to date
e.g. to_date('05 Dec 2000', 'DD Mon YYYY')
to_number(text, text) numeric convert string to numeric
e.g. to_number('12,454.8-', '99G999D9S')
to_timestamp(text, text) timestamp with time zone convert string to time stamp
e.g. to_timestamp('05 Dec 2000', 'DD Mon YYYY')
to_timestamp(double precision) timestamp with time zone convert Unix epoch to time stamp
e.g. to_timestamp(1284352323)

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.

Table 7-21 shows the template patterns available for formatting date and time values.

Table 7-21: 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)
SSSS 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 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
IYYY ISO year (4 and more digits)
IYY last 3 digits of ISO year
IY last 2 digits of ISO year
I last digit of ISO 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 ISO day of 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 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 ISO week number of year (01 - 53; the first Thursday of the new year is in week 1.)
CC century (2 digits) (The twenty-first century starts on 2001-01-01.)
J Julian Day (days since November 24, 4714 BC at midnight)
Q quarter (ignored by to_date and to_timestamp)
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 name
tz lower case time-zone name

Modifiers can be applied to any template pattern to alter its behavior. For example, FMMonth is the Month pattern with the FM modifier. Table 7-22 shows the modifier patterns for date/time formatting.

Table 7-22: Template Pattern Modifiers for Date/Time Formatting
Modifier Description
FM prefix fill mode (suppress padding blanks and zeroes)
e.g. FMMonth
TH suffix upper case ordinal number suffix
e.g. DDTH, e.g., 12TH
th suffix lower case ordinal number suffix
e.g. DDth, e.g., 12th
FX prefix fixed format global option (see usage notes)
e.g. FX Month DD Day
TM prefix translation mode (print localized day and month names based on lc_time)
e.g. TMMonth
SP suffix spell mode (not implemented)
e.g. DDSP

Usage notes for date/time formatting:

Table 7-23 shows the template patterns available for formatting numeric values.

Table 7-23: Template Patterns for Numeric Formatting
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 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 Roman numeral (input 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:

Certain modifiers can be applied to any template pattern to alter its behavior. For example, FM9999 is the 9999 pattern with the FM modifier. Table 7-24 shows the modifier patterns for numeric formatting.

Table 7-24: Template Pattern Modifiers for Numeric Formatting
Modifier Description
FM prefix fill mode (suppress padding blanks and zeroes)
e.g. FM9999
TH suffix upper case ordinal number suffix
e.g. 999TH
th suffix lower case ordinal number suffix
e.g. 999th

Table 7-25 shows some examples of the use of the to_char function.

Table 7-25: 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(-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, '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'
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