Mysterious in to_char

Question

Hi,
I am running a oracle query to get the values based on date by applying to_char and between dates.
For ex:
select veryfyDate,id,name from t1 where to_char(veryfyDate,'dd/mm/yyyy hh24:mi:ss') between to_char('01/01/2009 00:00:00','dd/mm/yyyy hh24:mi:ss') and to_char('05/01/2009 17:00:00','dd/mm/yyyy hh24:mi:ss')
what i was excepting the output would be the results will comes from the given date in the year 2009.
But after looking at output ,i surprised to see the dates that is coming from 2008 also
For ex:output
03/03/2008 manId manName
10/03/2008 manId1 manName1
02/01/2009 manId2 manName2
like this.
I knew that using to_date will amicably solve the issue.
But how to_char analyse and format the given char in a way that it could even fetch the date values from the year 2008.I surfed google and helpless.
1.How it converts date in char ?
2.How it compares the converted string or char in between ?
Thanx in Advance,
Prasad.

Answer 1

Paul M. wrote:
Doesn't matter which format you select, using TO_CHAR converts to a string and a string cannot be used for date comparisons.Ed,
do you mean it shouldn't be used, or you mean it won't work ?I mean it shouldn't be used.
If one were to go with "to_char(date_value,'yyyymmdd') then greater_than/less_than comparisons would work correctly, but it strikes me as lousy coding that should not be encouraged. Too often people will take code like that and not understand that it works only in a very specific instance for very specific reasons, then make incorrect assumptions and generalizations.