- publishing free software manuals
PostgreSQL Reference Manual - Volume 1 - SQL Language Reference
by The PostgreSQL Global Development Group
Paperback (6"x9"), 716 pages
ISBN 0954612027
RRP £32.00 ($49.95)

Sales of this book support the PostgreSQL project! Get a printed copy>>>

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.

The to_timestamp function can also take a single double precision argument to convert from Unix epoch 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(200120400)

In an output template string (for to_char), 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 (for anything but to_char), template patterns identify the parts of the input data string to be looked at and the values to be found there.

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 or A.M. or PM or P.M. meridian indicator (uppercase)
am or a.m. or pm or p.m. meridian indicator (lowercase)
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 digits of ISO year
BC or B.C. or AD or A.D. era indicator (uppercase)
bc or b.c. or ad or a.d. era indicator (lowercase)
MONTH full uppercase month name (blank-padded to 9 chars)
Month full mixed-case month name (blank-padded to 9 chars)
month full lowercase month name (blank-padded to 9 chars)
MON abbreviated uppercase month name (3 chars in English, localized lengths vary)
Mon abbreviated mixed-case month name (3 chars in English, localized lengths vary)
mon abbreviated lowercase month name (3 chars in English, localized lengths vary)
MM month number (01-12)
DAY full uppercase day name (blank-padded to 9 chars)
Day full mixed-case day name (blank-padded to 9 chars)
day full lowercase day name (blank-padded to 9 chars)
DY abbreviated uppercase day name (3 chars in English, localized lengths vary)
Dy abbreviated mixed-case day name (3 chars in English, localized lengths vary)
dy abbreviated lowercase day name (3 chars in English, localized lengths vary)
DDD day of year (001-366)
DD day of month (01-31)
D day of week (1-7; Sunday is 1)
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 (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 January 1, 4712 BC)
Q quarter
RM month in Roman numerals (I-XII; I=January) (uppercase)
rm month in Roman numerals (i-xii; i=January) (lowercase)
TZ time-zone name (uppercase)
tz time-zone name (lowercase)

Certain modifiers may 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 uppercase ordinal number suffix
e.g. DDTH
th suffix lowercase ordinal number suffix
e.g. DDth
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_messages)
e.g. TMMonth
SP suffix spell mode (not yet 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 scientific notation (not implemented yet)

Usage notes for numeric formatting:

Table 7-24 shows some examples of the use of the to_char function.

Table 7-24: 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'
ISBN 0954612027PostgreSQL Reference Manual - Volume 1 - SQL Language ReferenceSee the print edition