PostgreSQL 7.1.3 Documentation
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# 4.6. Formatting Functions

> Author: Written by Karel Zak (`<zakkr@zf.jcu.cz>`) 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 `9`s. 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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