Oracle CASE statement logic

Question

Hi all,
I have to compare the value of a varchar variable using a CASE statement and display the corresponding output.
But when the following code is being executed, and i gave the value of dayrange as anything other than number, i am getting the error;
The daysrange variable can be a number or a string (Hence i declared it as a varcahr2)
Error report:
ORA-06502: PL/SQL: numeric or value error: character to number conversion error
ORA-06512: at line 5
06502. 00000 - "PL/SQL: numeric or value error%s"
*Cause:   
*Action:
declare
daysrange varchar2(10):='abc';
x varchar2(100);
begin
CASE WHEN DAYSRANGE = 1 THEN x := 'LD';
          WHEN DAYSRANGE BETWEEN 2 AND 7 THEN x := 'LW';
          WHEN DAYSRANGE BETWEEN 8 AND 30 THEN x:= 'LM';
          WHEN DAYSRANGE BETWEEN 31 AND 90 THEN x:= 'L3M';
          WHEN DAYSRANGE BETWEEN 91 AND 180 THEN x:= 'L6M';
          WHEN DAYSRANGE BETWEEN 181 AND 365 THEN x:= 'LY';
          WHEN DAYSRANGE BETWEEN 366 AND 730 THEN x:= 'L2Y';
          WHEN DAYSRANGE > 730 THEN x:= 'O2Y';
     ELSE x:='x:= x';
     END case;--DATERANGE
exception
when case_not_found then
x:='something';
dbms_output.put_line(x);
end;
Edited by: Chaitanya on Nov 25, 2010 1:25 AM

Answer 1

Hi,
Chaitanya wrote:
... The daysrange variable can be a number or a string (Hence i declared it as a varcahr2)That's usually not a good design. It would be better to have two variables (or columns) if necessary, a VARCHAR2 and a NUMBER.
If you can't change the design, then test daysrange, and then do different things depending on whether it is a number or not.
For example:
declare
     daysrange      varchar2(10)     := '17';
     daysrange_n     NUMBER;
     x           varchar2(100);
begin
     IF  REGEXP_LIKE (daysrange, '^\d+$')
     THEN
          daysrange_n := TO_NUMBER (daysrange);
          x := CASE 
               WHEN daysrange_n > 730     THEN 'O2Y'
               WHEN daysrange_n > 365     THEN 'L2Y'
               WHEN daysrange_n > 180     THEN 'L1Y'
               WHEN daysrange_n >  90     THEN 'L6M'
               WHEN daysrange_n >  30     THEN 'L3M'
               WHEN daysrange_n >   7     THEN 'LM'
               WHEN daysrange_n >   1     THEN 'LW'
               WHEN daysrange_n =   1     THEN 'LD'
                              ELSE  x          -- If necessary
               END;
     END IF;
...The tests in a CASE expression are done in order. The n-th WHEN condition is tried only after conditions 1 through n have failed. That's why we can saY, for example,
"daysrange_n > 365" instead of
"daysrange_n BETWEEN 366 AND 730". If the 2nd test is even being performed, we know that the 1st test failed, and that daysrnage_n is not > 730.
I'm not saying that you have to write CASE expressions like this, or that it's necessarily better. You should know that it's possible, then choose whichever way makes the most sense in this situation.