*** Help needed regarding Query ***

Question

Hi,
I have the following input parameters as follows
in_col ( can have values as col1, col2, col3)
in_val
now i have the following requirement
select a,b
from tbl
where
<if in_col = col1 then tbl.a>
<if in_col = col2 then tbl.b>
<if in_col = col3 then tbl.c> -- tbl.c can have null values in the DB
IN
<if in_val = '*' and in_col = col3 then ('monday','tuesday',null) >
<else in_val >
-- That is the person can select a criteria ( in_col) which indicates a column name and also value for it ( in_val).
Now if he selects col1 or col2 then its a direct comparison with the in_val ( ie something like 'where column name = value' [ even the column name is dynamic here] )
but if he selects col3 and if in_value is any value other than '*' then also it will be a direct comparison ('where column name = value' ). But if he select col3 and in_value as '*' then the where clause should be like 'where tbl.C IN ('monday','tuesday',null) as col3 can contain null values also ( its like selecting all the rows(*) for col3)
Hope u r not confused...
Looking for a solution from you !!
S

Answer 1

I think of something like
   where  case in_col
          when 'col1' then a
          when 'col2' then b
          when 'col3' then nvl(c, 'null')
          end
          =
          case in_val
          when '*' then case in_col
                        when 'col3' then case c
                                         when 'monday' then 'monday'
                                         when 'tuesday' then 'tuesday'
                                         when 'null' then 'null'
                                         else 'xxxxxx'
                                         end
                        end
          else in_val
          end
not tested, neither syntactically, nor logically, nor in terms of performance!!
Regards,
Gerd