Error in converting varchar into dd/mm/yyyy

Question

Hi all,
i need to insert the "date_of_birth" in 'dd/mm/yyyy'.
but in master table "date_of_birth" column is in Varchar2(15),and values in the master tables are not in proper format.
i.e) some values are like *'21-jan-1988'*,
and some are like *'01/21/1988'* and *'21-01-1988'*.
i need to insert into a new table in dd/mm/yyyy format.
thanks in advance.

Answer 1

You could use such a method, but WITH NOT GUARANTEE AT ALL_ that you're not inserting WRONG_ dates of birth.SQL> with rotten_data as (
  2  -- start of sample data --
  3  select '10-Jan-2010' vdate from dual
  4  union all select '10/Feb/2010' from dual
  5  union all select '10-03-2010' from dual
  6  union all select '10/04/2010' from dual
  7  union all select '17/04/2010' from dual
  8  union all select '11/14/2010' from dual
  9  union all select '23-04-2010' from dual
10  union all select '07-18-2010' from dual
11  union all select '01-02-2010' from dual
12  -- end of sample data --
13  )
14  select
15     vdate,
16     case
17             when regexp_like(r2,'^\D*$') then to_date(r1||r2||yr,'ddMonyyyy')
18             when regexp_like(r1,'^\D*$') then to_date(r2||r1||yr,'ddMonyyyy')
19             when (to_number(r1)>12 and to_number(r2)<=12) then to_date(r1||r2||yr,'ddmmyyyy')
20             when (to_number(r1)<=12 and to_number(r2)>12) then to_date(r2||r1||yr,'ddmmyyyy')
21             else to_date(r1||r2||yr,'ddmmyyyy')
22     end newdt
23  from (
24     select
25             vdate
26             ,regexp_substr(vdate,'[^-/]+',1,1) r1
27             ,regexp_substr(vdate,'[^-/]+',1,2) r2
28             ,regexp_substr(vdate,'[^-/]{4}',1,1)yr
29     from rotten_data
30  ) ;
VDATE       NEWDT
10-Jan-2010 10/01/2010 00:00:00
10/Feb/2010 10/02/2010 00:00:00
10-03-2010  10/03/2010 00:00:00
10/04/2010  10/04/2010 00:00:00
17/04/2010  17/04/2010 00:00:00
11/14/2010  14/11/2010 00:00:00
23-04-2010  23/04/2010 00:00:00
07-18-2010  18/07/2010 00:00:00
01-02-2010  01/02/2010 00:00:00
9 rows selected.This would still fail if the data is not one of those format +(or is not a valid date whatever the format)+ :
- dd/mm/yyyy
- mm/dd/yyyy
- dd-mm-yyyy
- mm-dd-yyyy
- dd-Mon-yyyy
- dd/Mon/yyyy
if one of the value is > 12 then it consider it as the day, the other one being the month.
If both are <=12, then it assumes the first is the day (dd).
Without any additionnal information, you cannot really make it better...