Oracle case inside where clause

This is a simple question, I’ve read some details about using CASE in WHERE clause, but couldn’t able to make a clear idea how to use it. The below is my sample query:

1    SELECT * FROM dual
2    WHERE (1 =1)
3     AND (SYSDATE+1 > SYSDATE)
4     AND (30 > 40)
5     AND (25 < 35);

I have a procedure i_value as in parameter. I need to ignore the 4th line if i_value is ‘S’ and I need to ignore the 5th line if i_value is ‘T’.

Thanks in advance.

Answer

I think this is the best way to solve your problem:

select *
from dual
where (1 = 1)
      and (sysdate + 1 > sysdate)
      and case
            when i_value = 'S'
              then
                case
                  when (25 < 35)
                    then 1
                    else 0
                end
            when i_value = 'T'
              then
                case
                  when (30 > 40)
                    then 1
                    else 0
                end
          end = 1;

Of course, you could use Dynamic SQL, but it’d be more difficult and less effective.