Question

Hi I have the following function created in Oracle.
i will have to pass date-1 and date-2 parameters into the function and the function should return the another date to me .

please see the code below.

create or replace function GETD(p_d1   in date, 
                                p_d2   in date ) return DATE 
   as 
       l_result    DATE; 
   begin 
    SELECT EDIT_Date into l_result FROM qa.employees  WHERE qa.employee_join_date BETWEEN TO_DATE(p_d1, 'MM/DD/YYYY') AND TO_DATE(p_d2, 'MM/DD/YYYY') AND ROWNUM <= 1
    ;
       return l_result; 
  end; 

i execute the function as below

SELECT GETD('27-JUN-12','28-JUN-12') FROM DUAL

the function get compiled and while im passing the parameters to execute the function i get the following error “Not a Valid Month”.
Could some one please tell me where im going wrong

thanks
Justin

Answer 1

First, you should not call TO_DATE on a date variable. If you do that, you force Oracle to first convert the date to a string using the session’s NLS_DATE_FORMAT and then convert the string back to a date using the specified format mask. If your NLS_DATE_FORMAT happens not to match the specified format mask (and, since the NLS_DATE_FORMAT is controlled by the client, some users and sessions will inevitably have a different date format), you’ll get an error.

Assuming your intention was merely to ignore any time component, you should be using the trunc function instead.

create or replace function GETD(p_d1   in date, 
                                p_d2   in date ) 
  return DATE 
as 
  l_result    DATE; 
begin 
  SELECT EDIT_Date 
    into l_result 
    FROM qa.employees  
   WHERE qa.employee_join_date BETWEEN trunc(p_d1) AND trunc(p_d2) 
     AND ROWNUM <= 1;

  return l_result; 
end; 

The presence of a rownum <= 1 condition seems a bit odd– it seems unlikely that you really want to fetch an arbitrary row from the table that matches the employee_join_date criteria. Not knowing the requirements, it seems likely that you want to do something deterministic that fetches the row with the minimum (or maximum) edit_date.

Second, when you call the function, you should pass in DATE parameters rather than passing in strings and letting Oracle implicitly convert the strings to dates using the session’s NLS_DATE_FORMAT. If you use date literals

SELECT GETD(date '2012-06-27', date '2012-06-28') 
  FROM DUAL

or convert the strings to dates explicitly using a TO_DATE

SELECT GETD(to_date('27-JUN-12', 'DD-MON-RR'), to_date('28-JUN-12', 'DD-MON-RR')) 
  FROM DUAL

then your call will work regardless of the client’s NLS_DATE_FORMAT.