Value

A number or date that will be converted to a string.

format_mask

Optional. This is the format that will be used to convert value to a string.

nls_language

Optional. This is the nls language used to convert value to a string.

Numbers

TO_CHAR(1210.73, ‘9999.9‘)
Result: ‘ 1210.7‘

TO_CHAR(-1210.73, ‘9999.9‘)
Result: ‘-1210.7‘

TO_CHAR(1210.73, ‘9,999.99‘)
Result: ‘ 1,210.73‘

TO_CHAR(1210.73, ‘$9,999.00‘)
Result: ‘ $1,210.73‘

TO_CHAR(21, ‘000099‘)
Result: ‘ 000021‘

Dates

TO_CHAR(sysdate, ‘yyyy/mm/dd‘)
Result: ‘2003/07/09‘

TO_CHAR(sysdate, ‘Month DD, YYYY‘)
Result: ‘July 09, 2003‘

TO_CHAR(sysdate, ‘FMMonth DD, YYYY‘)
Result: ‘July 9, 2003‘

TO_CHAR(sysdate, ‘MON DDth, YYYY‘)
Result: ‘JUL 09TH, 2003‘

TO_CHAR(sysdate, ‘FMMON DDth, YYYY‘)
Result: ‘JUL 9TH, 2003‘

TO_CHAR(sysdate, ‘FMMon ddth, YYYY‘)
Result: ‘Jul 9th, 2003‘

"FM":This means that zeros and blanks are suppressed(压制).

Parameter

Explanation

YEAR

Year, spelled out

YYYY

4-digit year

YYY

YY

Y

Last 3, 2, or 1 digit(s) of year.

IYY

IY

I

Last 3, 2, or 1 digit(s) of ISO year.

IYYY

4-digit year based on the ISO standard

Q

Quarter of year (1, 2, 3, 4; JAN-MAR = 1).

MM

Month (01-12; JAN = 01).

MON

Abbreviated name of month.

MONTH

Name of month, padded with blanks to length of 9 characters.

RM

Roman numeral month (I-XII; JAN = I).

WW

Week of year (1-53) where week 1 starts on the first day of the year and continues to the seventh day of the year.

W

Week of month (1-5) where week 1 starts on the first day of the month and ends on the seventh.

IW

Week of year (1-52 or 1-53) based on the ISO standard.

D

Day of week (1-7).

DAY

Name of day.

DD

Day of month (1-31).

DDD

Day of year (1-366).

DY

Abbreviated name of day.

J

Julian day; the number of days since January 1, 4712 BC.

HH

Hour of day (1-12).

HH12

Hour of day (1-12).

HH24

Hour of day (0-23).

MI

Minute (0-59).

SS

Second (0-59).

SSSSS

Seconds past midnight (0-86399).

FF

Fractional seconds.

Question: Why doesn‘t this sort the days of the week in order?

Answer: In the above SQL, the fmDay format mask used in the TO_CHAR function will return the name of the Day and not the numeric value of the day.

To sort the days of the week in order, you need to return the numeric value of the day by using the fmD format mask as follows:

SELECT ename, hiredate, TO_CHAR((hiredate),‘fmDay‘) "Day"
FROM emp
ORDER BY "Day";

SELECT ename, hiredate, TO_CHAR((hiredate),‘fmD‘) "Day"
FROM emp
ORDER BY "Day";