Format Models

A format model is a character literal that describes the format of DATE or NUMBER data stored in a character string. When you convert a character string into a date or number, a format model tells Oracle how to interpret the string. In SQL statements, you can use a format model as an argument of the TO_CHAR and TO_DATE functions:

• To specify the format for Oracle to use to return a value from the database
• To specify the format for a value you have specified for Oracle to store in the database

  Note: A format model does not change the internal representation of the value in the database.

For example,

• The date format model for the string '17:45:29' is 'HH24:MI:SS'.
• The date format model for the string '11-Nov-1999' is 'DD-Mon-YYYY'.
• The number format model for the string '$2,304.25' is '$9,999.99'.

For lists of date and number format model elements, see Table 2-13, " Number Format Elements" and Table 2-15, " Datetime Format Elements".

The values of some formats are determined by the value of initialization parameters. For such formats, you can specify the characters returned by these format elements implicitly using the initialization parameter NLS_TERRITORY. You can change the default date format for your session with the ALTER SESSION statement.

Format of Return Values: Examples

You can use a format model to specify the format for Oracle to use to return values from the database to you.

The following statement selects the salaries of the employees in Department 80 and uses the TO_CHAR function to convert these salaries into character values with the format specified by the number format model '$9,990.99':

SELECT last_name employee, TO_CHAR(salary, '$99,990.99')
   FROM employees
   WHERE department_id = 80;
 

Because of this format model, Oracle returns salaries with leading dollar signs, commas every three digits, and two decimal places.

The following statement selects the date on which each employee from Department 20 was hired and uses the TO_CHAR function to convert these dates to character strings with the format specified by the date format model 'fmMonth DD, YYYY':

SELECT last_name employee, 
    TO_CHAR(hire_date,'fmMonth DD, YYYY') hiredate
    FROM employees
    WHERE department_id = 20;

With this format model, Oracle returns the hire dates (as specified by "fm") without blank padding, two digits for the day, and the century included in the year.

Supplying the Correct Format Model: Examples

When you insert or update a column value, the datatype of the value that you specify must correspond to the column's datatype. You can use format models to specify the format of a value that you are converting from one datatype to another datatype required for a column.

For example, a value that you insert into a DATE column must be a value of the DATE datatype or a character string in the default date format (Oracle implicitly converts character strings in the default date format to the DATE datatype). If the value is in another format, then you must use the TO_DATE function to convert the value to the DATE datatype. You must also use a format model to specify the format of the character string.

The following statement updates Hunold's hire date using the TO_DATE function with the format mask 'YYYY MM DD' to convert the character string '1998 05 20' to a DATE value:

UPDATE employees 
  SET hire_date = TO_DATE('1998 05 20','YYYY MM DD') 
  WHERE last_name = 'Hunold'; 

This remainder of this section describes how to use:

• Number Format Models
• Date Format Models
• Format Model Modifiers

  See Also: TO_CHAR (datetime), TO_CHAR (number), and TO_DATE

Number Format Models

You can use number format models:

• In the TO_CHAR function to translate a value of NUMBER datatype to VARCHAR2 datatype
• In the TO_NUMBER function to translate a value of CHAR or VARCHAR2 datatype to NUMBER datatype

All number format models cause the number to be rounded to the specified number of significant digits. If a value has more significant digits to the left of the decimal place than are specified in the format, then pound signs (#) replace the value. If a positive value is extremely large and cannot be represented in the specified format, then the infinity sign (~) replaces the value. Likewise, if a negative value is extremely small and cannot be represented by the specified format, then the negative infinity sign replaces the value (-~). This event typically occurs when you are using TO_CHAR with a restrictive number format string, causing a rounding operation.

Number Format Elements

A number format model is composed of one or more number format elements. Table 2-13 lists the elements of a number format model. Examples are shown in Table 2-14.

Negative return values automatically contain a leading negative sign and positive values automatically contain a leading space unless the format model contains the MI, S, or PR format element.

Table 2-13  Number Format Elements

Table 2-14 shows the results of the following query for different values of number and 'fmt':

SELECT TO_CHAR(number, 'fmt')
   FROM DUAL;

Table 2-14   Results of Example Number Conversions

Date Format Models

You can use date format models:

• In the TO_* datetime function to translate a character value that is in a format other than the default date format into a DATE value. (The TO_* datetime functions are TO_CHAR, TO_DATE, TO_TIMESTAMP, TO_TIMESTAMP_TZ, TO_YMINTERVAL, and TO_DSINTERVAL.)
• In the TO_CHAR function to translate a DATE value that is in a format other than the default date format into a string (for example, to print the date from an application)

The total length of a date format model cannot exceed 22 characters.

The default date format is specified either explicitly with the initialization parameter NLS_DATE_FORMAT or implicitly with the initialization parameter NLS_TERRITORY. You can change the default date format for your session with the ALTER SESSION statement.

Date Format Elements

A date format model is composed of one or more datetime format elements as listed in Table 2-15.

• For input format models, format items cannot appear twice, and format items that represent similar information cannot be combined. For example, you cannot use 'SYYYY' and 'BC' in the same format string.
• Some of the datetime format elements cannot be used in the TO_* datetime functions, as noted in Table 2-15.
• The following datetime format elements can be used in interval and timestamp format models, but not in the original DATE format model: FF, TZD, TZH, TZM, and TZR.

Capitalization of Date Format Elements

Capitalization in a spelled-out word, abbreviation, or Roman numeral follows capitalization in the corresponding format element. For example, the date format model 'DAY' produces capitalized words like 'MONDAY'; 'Day' produces 'Monday'; and 'day' produces 'monday'.

Punctuation and Character Literals in Date Format Models

You can also include these characters in a date format model:

• Punctuation such as hyphens, slashes, commas, periods, and colons
• Character literals, enclosed in double quotation marks

These characters appear in the return value in the same location as they appear in the format model.

Table 2-15  Datetime Format Elements

-
/
,
.
;
:
"text"

AD
A.D.

AM
A.M.

BC
B.C.

CC
SCC

D

DAY

DD

DDD

DY

E

EE

FF [1..9]

HH

HH12

HH24

IW

IYY
IY
I

IYYY

J

MI

MM

MON

MONTH

PM
P.M.

Q

RM

RR

RRRR

SS

SSSSS

TZD 

TZH

TZM

TZR

WW

W

X

Y,YYY

YEAR
SYEAR

YYYY
SYYYY

YYY
YY
Y

Oracle returns an error if an alphanumeric character is found in the date string where punctuation character is found in the format string. For example:

TO_CHAR (TO_DATE('0297','MM/YY'), 'MM/YY')

returns an error.

Date Format Elements and Globalization Support

The functionality of some datetime format elements depends on the country and language in which you are using Oracle. For example, these datetime format elements return spelled values:

• MONTH
• MON
• DAY
• DY
• BC or AD or B.C. or A.D.
• AM or PM or A.M or P.M.

The language in which these values are returned is specified either explicitly with the initialization parameter NLS_DATE_LANGUAGE or implicitly with the initialization parameter NLS_LANGUAGE. The values returned by the YEAR and SYEAR datetime format elements are always in English.

The datetime format element D returns the number of the day of the week (1-7). The day of the week that is numbered 1 is specified implicitly by the initialization parameter NLS_TERRITORY.

ISO Standard Date Format Elements

Oracle calculates the values returned by the datetime format elements IYYY, IYY, IY, I, and IW according to the ISO standard. For information on the differences between these values and those returned by the datetime format elements YYYY, YYY, YY, Y, and WW, see the discussion of Globalization Support in Oracle9i Database Globalization Support Guide.

The RR Date Format Element

The RR datetime format element is similar to the YY datetime format element, but it provides additional flexibility for storing date values in other centuries. The RR datetime format element lets you store 20th century dates in the 21st century by specifying only the last two digits of the year.

If you use the TO_DATE function with the YY datetime format element, then the year returned always has the same first 2 digits as the current year. If you use the RR datetime format element instead, then the century of the return value varies according to the specified two-digit year and the last two digits of the current year. That is:

• If the specified two-digit year is 00 to 49, then
  • If the last two digits of the current year are 00 to 49, then the returned year has the same first two digits as the current year.
  • If the last two digits of the current year are 50 to 99, then the first 2 digits of the returned year are 1 greater than the first 2 digits of the current year.
• If the specified two-digit year is 50 to 99, then
  • If the last two digits of the current year are 00 to 49, then the first 2 digits of the returned year are 1 less than the first 2 digits of the current year.
  • If the last two digits of the current year are 50 to 99, then the returned year has the same first two digits as the current year.

The following examples demonstrate the behavior of the RR datetime format element.

RR Date Format Examples

Assume these queries are issued between 1950 and 1999:

SELECT TO_CHAR(TO_DATE('27-OCT-98', 'DD-MON-RR') ,'YYYY') "Year"
   FROM DUAL;

Year
----
1998

SELECT TO_CHAR(TO_DATE('27-OCT-17', 'DD-MON-RR') ,'YYYY') "Year"
   FROM DUAL; 

Year
----
2017

Now assume these queries are issued between 2000 and 2049:

SELECT TO_CHAR(TO_DATE('27-OCT-98', 'DD-MON-RR') ,'YYYY') "Year"
   FROM DUAL; 

Year
----
1998 

SELECT TO_CHAR(TO_DATE('27-OCT-17', 'DD-MON-RR') ,'YYYY') "Year"
   FROM DUAL; 

Year
----
2017

Note that the queries return the same values regardless of whether they are issued before or after the year 2000. The RR datetime format element lets you write SQL statements that will return the same values from years whose first two digits are different.

Date Format Element Suffixes

Table 2-17 lists suffixes that can be added to datetime format elements:

Table 2-16 Date Format Element Suffixes

Format Model Modifiers

The FM and FX modifiers, used in format models in the TO_CHAR function, control blank padding and exact format checking.

A modifier can appear in a format model more than once. In such a case, each subsequent occurrence toggles the effects of the modifier. Its effects are enabled for the portion of the model following its first occurrence, and then disabled for the portion following its second, and then reenabled for the portion following its third, and so on.

FM

"Fill mode". This modifier suppresses blank padding in the return value of the TO_CHAR function:

• In a datetime format element of a TO_CHAR function, this modifier suppresses blanks in subsequent character elements (such as MONTH) and suppresses leading zeroes for subsequent number elements (such as MI) in a date format model. Without FM, the result of a character element is always right padded with blanks to a fixed length, and leading zeroes are always returned for a number element. With FM, because there is no blank padding, the length of the return value may vary.
• In a number format element of a TO_CHAR function, this modifier suppresses blanks added to the left of the number, so that the result is left-justified in the output buffer. Without FM, the result is always right-justified in the buffer, resulting in blank-padding to the left of the number.

FX

"Format exact". This modifier specifies exact matching for the character argument and date format model of a TO_DATE function:

• Punctuation and quoted text in the character argument must exactly match (except for case) the corresponding parts of the format model.
• The character argument cannot have extra blanks. Without FX, Oracle ignores extra blanks.
• Numeric data in the character argument must have the same number of digits as the corresponding element in the format model. Without FX, numbers in the character argument can omit leading zeroes.

  When FX is enabled, you can disable this check for leading zeroes by using the FM modifier as well.

If any portion of the character argument violates any of these conditions, then Oracle returns an error message.

Format Modifier Examples

The following statement uses a date format model to return a character expression:

SELECT TO_CHAR(SYSDATE, 'fmDDTH')||' of '||TO_CHAR
   (SYSDATE, 'fmMonth')||', '||TO_CHAR(SYSDATE, 'YYYY') "Ides" 
    FROM DUAL; 

Ides 
------------------ 
3RD of April, 1998

The preceding statement also uses the FM modifier. If FM is omitted, then the month is blank-padded to nine characters:

SELECT TO_CHAR(SYSDATE, 'DDTH')||' of '||
   TO_CHAR(SYSDATE, 'Month')||', '||
   TO_CHAR(SYSDATE, 'YYYY') "Ides"
   FROM DUAL; 

Ides 
----------------------- 
03RD of April    , 1998 

The following statement places a single quotation mark in the return value by using a date format model that includes two consecutive single quotation marks:

SELECT TO_CHAR(SYSDATE, 'fmDay')||'''s Special' "Menu"
   FROM DUAL; 

Menu 
----------------- 
Tuesday's Special 

Two consecutive single quotation marks can be used for the same purpose within a character literal in a format model.

Table 2-18 shows whether the following statement meets the matching conditions for different values of char and 'fmt' using FX (the table named table has a column date_column of datatype DATE):

UPDATE table 
  SET date_column = TO_DATE(char, 'fmt');

Table 2-17  Matching Character Data and Format Models with the FX Format Model Modifier

String-to-Date Conversion Rules

The following additional formatting rules apply when converting string values to date values (unless you have used the FX or FXFM modifiers in the format model to control exact format checking):

• You can omit punctuation included in the format string from the date string if all the digits of the numerical format elements, including leading zeros, are specified. In other words, specify 02 and not 2 for two-digit format elements such as MM, DD, and YY.
• You can omit time fields found at the end of a format string from the date string.
• If a match fails between a datetime format element and the corresponding characters in the date string, then Oracle attempts alternative format elements, as shown in Table 2-19.

  Table 2-18  Oracle Format Matching

  Original Format Element	Additional Format Elements to Try in Place of the Original
  'MM'	'MON' and 'MONTH'
  'MON	'MONTH'
  'MONTH'	'MON'
  'YY'	'YYYY'
  'RR'	'RRRR'

XML Format Model

The SYS_XMLGEN function returns an instance of type XMLType containing an XML document. Oracle provides the XMLFormat object, which lets you format the output of the SYS_XMLGEN function.

Table 2-20 lists and describes the attributes of the XMLFormat object. The function that implements this type follows the table.

Table 2-19  Attributes of the XMLFormat Object

The function that implements the XMLFormat object follows:

  STATIC FUNCTION createFormat(
     enclTag IN varchar2 := 'ROWSET',
     schemaType IN varchar2 := 'NO_SCHEMA',
     schemaName IN varchar2 := null,
     targetNameSpace IN varchar2 := null,
     dburlPrefix IN varchar2 := null, 
     processingIns IN varchar2 := null) RETURN XMLGenFormatType,
  MEMBER PROCEDURE genSchema (spec IN varchar2),
  MEMBER PROCEDURE setSchemaName(schemaName IN varchar2),
  MEMBER PROCEDURE setTargetNameSpace(targetNameSpace IN varchar2),
  MEMBER PROCEDURE setEnclosingElementName(enclTag IN varchar2), 
  MEMBER PROCEDURE setDbUrlPrefix(prefix IN varchar2),
  MEMBER PROCEDURE setProcessingIns(pi IN varchar2),
  CONSTRUCTOR FUNCTION XMLGenFormatType (
     enclTag IN varchar2 := 'ROWSET',
     schemaType IN varchar2 := 'NO_SCHEMA',
     schemaName IN varchar2 := null,
     targetNameSpace IN varchar2 := null,
     dbUrlPrefix IN varchar2 := null, 
     processingIns IN varchar2 := null) RETURN SELF AS RESULT