29

Example:

select ename from emp where hiredate = todate('01/05/81','dd/mm/yy')

and 

select ename from emp where hiredate = todate('01/05/81','dd/mm/rr')

return different results

juan
  • 80,295
  • 52
  • 162
  • 195

6 Answers6

47

http://oracle.ittoolbox.com/groups/technical-functional/oracle-dev-l/difference-between-yyyy-and-rrrr-format-519525

YY allows you to retrieve just two digits of a year, for example, the 99 in 1999. The other digits (19) are automatically assigned to the current century. RR converts two-digit years into four-digit years by rounding.

50-99 are stored as 1950-1999, and dates ending in 00-49 are stored as 2000-2049. RRRR accepts a four-digit input (although not required), and converts two-digit dates as RR does. YYYY accepts 4-digit inputs butdoesn't do any date converting

Essentially, your first example will assume that 81 is 2081 whereas the RR one assumes 1981. So the first example should not return any rows as you most likely did not hire any guys after May 1 2081 yet :-)

Michael Stum
  • 177,530
  • 117
  • 400
  • 535
5

y2k compatibility. rr assumes 01 to be 2001, yy assumes 01 to be 1901

see: http://www.oradev.com/oracle_date_format.jsp

edit: damn! michael "quickfingers" stum beat me to it!

/mp

Community
  • 1
  • 1
mauriciopastrana
  • 5,010
  • 7
  • 35
  • 36
5

@Michael Stum

My last Oracle experience is a bit long ago

uhm, was it, before 2000? :p

...

Will yy always assume 19xx?

according to your source, we get the following scenarios:

USING
ENTERED
STORED
SELECT of date column


YY
22-FEB-01
22-FEB-1901
22-FEB-01


YYYY
22-FEB-01
22-FEB-0001
22-FEB-0001


RR
22-FEB-01
22-FEB-2001
22-FEB-01


RRRR
22-FEB-01
22-FEB-2001
22-FEB-2001

/mp

Community
  • 1
  • 1
mauriciopastrana
  • 5,010
  • 7
  • 35
  • 36
2

RR displays four digits as 1999 or 2015(if it is <49 then it will consider 20th century)

hariharan
  • 21
  • 1
0

About RR or RRRR

When we are inserting the dates with 2 digits years (i.e. 09/oct/15) then Oracle may changes the centuries automatically hence the solution is 4 digit dates. But 4 digit version is introduced in some recent versions, therefore the solutions for this problem in earlier versions was RR or RRRR. But note that it only works with the TO_DATE() function but not with the TO_CHAR() function.

Whenever inserts/updates are conducted upon dates we should always clarify current date running in the clock in association with the date translation since Oracle conducts every date translation by contacting the server.

In order to keep the consistencies among the centuries, it is always better to execute the date translation with 4 digit years.

About YY or YYYY

It accepts the dates but doesn't has functionality to automatically change it.

This Image shows behaviour when inserting date with two digit (i.e. 09/oct/15)

beaver
  • 523
  • 1
  • 9
  • 20
Pritam Bhansali
  • 1
  • 4
-1

RR stands for after 1990 and yy assumes 90 as 2090....as we are in the current yr,...

vivek
  • 47
  • 1
  • 5
  • 1
    Nope... `rr` is different depending on whether you are [before the 50th year of the century](http://docs.oracle.com/cd/E11882_01/server.112/e26088/sql_elements004.htm#i116004) or not. – Ben Nov 18 '12 at 18:10