Date column is throwing error in my query.

Question

select (to_date(((to_char(to_date('6/27/1980','mm/dd/rrrr'),'DD/MM'))||'/' ||
((to_char(sysdate,'rrrr'))- (to_char(to_date('6/27/1980','mm/dd/rrrr'),'rrrr'))
+(to_char(to_date('6/27/1980','mm/dd/rrrr'),'rrrr')))),'DD/MM/yyyy')) current_dob from M_CUSTOMER_HDR
This query is working.
select (to_date(((to_char(to_date(cust_Dob,'mm/dd/rrrr'),'DD/MM'))||'/' ||
((to_char(sysdate,'rrrr'))- (to_char(to_date(cust_Dob,'mm/dd/rrrr'),'rrrr'))
+(to_char(to_date(cust_Dob,'mm/dd/rrrr'),'rrrr')))),'DD/MM/yyyy')) current_dob from M_CUSTOMER_HDR
This query is getting error:-
a non-numeric character was found where a numeric was expected
all data in table is following same date formate.but null values are also available in column.
can any body help me in this query. thanks in advance..

Answer 1

Null gives the problem:
SQL> with M_CUSTOMER_HDR as (
  2  --  select '6/27/1980' as cust_dob from dual
  3    select null as cust_dob from dual
  4  )
  5  select (
  6    to_date(
  7      (
  8        (to_char(to_date(cust_Dob,'mm/dd/rrrr'),'DD/MM'))
  9        ||'/' ||
10        (
11          (to_char(sysdate,'rrrr'))
12          - (to_char(to_date(cust_Dob,'mm/dd/rrrr'),'rrrr'))
13          + (to_char(to_date(cust_Dob,'mm/dd/rrrr'),'rrrr'))
14        )
15      )
16      ,'DD/MM/yyyy'
17    )) current_dob
18  from M_CUSTOMER_HDR
19  ;
      ||'/' ||
ERROR at line 9:
ORA-01858: a non-numeric character was found where a numeric was expected
SQL> with M_CUSTOMER_HDR as (
  2  --  select '6/27/1980' as cust_dob from dual
  3    select null as cust_dob from dual
  4  )
  5  select --(
  6  --  to_date(
  7      (
  8        (to_char(to_date(cust_Dob,'mm/dd/rrrr'),'DD/MM'))
  9        ||'/' ||
10        (
11          (to_char(sysdate,'rrrr'))
12          - (to_char(to_date(cust_Dob,'mm/dd/rrrr'),'rrrr'))
13          + (to_char(to_date(cust_Dob,'mm/dd/rrrr'),'rrrr'))
14        )
15      )
16  --    ,'DD/MM/yyyy'
17  --  )) current_dob
18  from M_CUSTOMER_HDR
19  ;
((TO_CHAR(TO_DATE(CUST_DOB,'MM/DD/RRRR'),'DD/M
/'/' is not a date in 'DD/MM/YYYY' format ;).
Note also that expression "- (to_char(to_date(cust_Dob,'mm/dd/rrrr'),'rrrr')) + (to_char(to_date(cust_Dob,'mm/dd/rrrr'),'rrrr'))" is always evaluates to 0 (or null if cust_dob is null).
Regards,
Dima