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 9.20, “Formatting Functions” 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 9.20. Formatting Functions
| Function | Return Type | Description | Example |
|---|---|---|---|
|
text |
convert time stamp to string | to_char(current_timestamp, 'HH12:MI:SS') |
|
text |
convert interval to string | to_char(interval '15h 2m 12s', 'HH24:MI:SS') |
|
text |
convert integer to string | to_char(125, '999') |
|
text |
convert real/double precision to string | to_char(125.8::real, '999D9') |
|
text |
convert numeric to string | to_char(-125.8, '999D99S') |
|
date |
convert string to date | to_date('05 Dec 2000', 'DD Mon YYYY') |
|
timestamp with time zone |
convert string to time stamp | to_timestamp('05 Dec 2000', 'DD Mon YYYY') |
|
timestamp with time zone |
convert UNIX epoch to time stamp | to_timestamp(200120400) |
|
numeric |
convert string to numeric | to_number('12,454.8-', '99G999D9S') |
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 9.21, “Template Patterns for Date/Time Formatting” shows the template patterns available for formatting date and time values.
Table 9.21. 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) |
Mon |
abbreviated mixed-case month name (3 chars) |
mon |
abbreviated lowercase month name (3 chars) |
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) |
Dy |
abbreviated mixed-case day name (3 chars) |
dy |
abbreviated lowercase day name (3 chars) |
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) |
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 9.22, “Template Pattern Modifiers for Date/Time Formatting” shows the
modifier patterns for date/time formatting.
Table 9.22. Template Pattern Modifiers for Date/Time Formatting
| Modifier | Description | Example |
|---|---|---|
FM prefix |
fill mode (suppress padding blanks and zeroes) | FMMonth |
TH suffix |
uppercase ordinal number suffix | DDTH |
th suffix |
lowercase ordinal number suffix | DDth |
FX prefix |
fixed format global option (see usage notes) | FX Month DD Day |
SP suffix |
spell mode (not yet 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.
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 correct, but
to_timestamp('2000 JUN', 'FXYYYY MON') returns an error,
because to_timestamp expects one space only.
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 key words. For example, in
'"Hello Year "YYYY', the YYYY
will be replaced by the year data, but the single Y in Year
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\\"'.
(Two backslashes are necessary because the backslash already
has a special meaning in a string constant.)
The YYYY conversion from string to timestamp or
date has a restriction 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 the year 20000):
to_date('200001131', 'YYYYMMDD') will be
interpreted as a 4-digit year; instead use a non-digit
separator after the year, like
to_date('20000-1131', 'YYYY-MMDD') or
to_date('20000Nov31', 'YYYYMonDD').
In conversions from string to timestamp or
date, the CC field is ignored if there
is a YYY, YYYY or
Y,YYY field. If CC is used with
YY or Y then the year is computed
as (CC-1)*100+YY.
Millisecond (MS) and microsecond (US)
values in a conversion from string to timestamp are used as part of the
seconds after the decimal point. For example
to_timestamp('12:3', 'SS:MS') is not 3 milliseconds,
but 300, because the conversion counts it as 12 + 0.3 seconds.
This means 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 use
12:003, which the conversion counts as
12 + 0.003 = 12.003 seconds.
Here is a more
complex example:
to_timestamp('15:12:02.020.001230', 'HH:MI:SS.MS.US')
is 15 hours, 12 minutes, and 2 seconds + 20 milliseconds +
1230 microseconds = 2.021230 seconds.
to_char's day of the week numbering
(see the 'D' formatting pattern) is different from that of the
extract function.
to_char(interval) formats HH and
HH12 as hours in a single day, while HH24
can output hours exceeding a single day, e.g. >24.
Table 9.23, “Template Patterns for Numeric Formatting” shows the template patterns available for formatting numeric values.
Table 9.23. 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:
A sign formatted using SG, PL, or
MI is not anchored to
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 results in a value with the same number of
digits as there are 9s. If a digit is
not available it outputs a space.
TH does not convert values less than zero
and does not convert fractional numbers.
PL, SG, and
TH are PostgreSQL
extensions.
V effectively
multiplies the input values by
10^, where
nn 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 9.24, “to_char Examples” shows some
examples of the use of the to_char function.
Table 9.24. 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' |