Conditional operator in where clause?

Question

I have 4 assignable parameters for filtering records. If a parameter is not assigned the filter is ignored. This is working fine with the SQL-statement below except for one scenario: if none of the parameters are assigned I get no records at all but then I need all of the records.
with t as
    select 1 as val, 'a' as var from dual union all
    select 2 as val, 'a' as var from dual union all
    select 3 as val, 'b' as var from dual union all
    select 4 as val, 'b' as var from dual union all
    select 5 as val, 'b' as var from dual union all
    select 6 as val, 'c' as var from dual union all
    select 7 as val, 'd' as var from dual union all
    select 8 as val, 'e' as var from dual union all
    select 9 as val, 'e' as var from dual union all
    select 0 as val, 'f' as var from dual
select *
from t
where t.var = decode(:pvar1,'',null,:pvar1)
or t.var = decode(:pvar2,'',null,:pvar2)
or t.var = decode(:pvar3,'',null,:pvar3)
or t.var = decode(:pvar4,'',null,:pvar4)

Answer 1

You need no "OR"s
<br>
SQL> var pvar1 char
SQL> var pvar2 char
SQL> var pvar3 char
SQL> var pvar4 char
SQL> with t as(    select 1 as val, 'a' as var from dual union all
  2      select 2 as val, 'a' as var from dual union all
  3      select 3 as val, 'b' as var from dual union all
  4      select 4 as val, 'b' as var from dual union all
  5      select 5 as val, 'b' as var from dual union all
  6      select 6 as val, 'c' as var from dual union all
  7      select 7 as val, 'd' as var from dual union all
  8      select 8 as val, 'e' as var from dual union all
  9      select 9 as val, 'e' as var from dual union all
10      select 0 as val, 'f' as var from dual)
11  select *from t
12  where t.var = coalesce(:pvar1,:pvar2,:pvar3,:pvar4,t.var);
       VAL V
         1 a
         2 a
         3 b
         4 b
         5 b
         6 c
         7 d
         8 e
         9 e
         0 f
10 rows selected.
SQL> exec :pvar4 := 'b';
PL/SQL procedure successfully completed.
SQL>  with t as(    select 1 as val, 'a' as var from dual union all
  2       select 2 as val, 'a' as var from dual union all
  3       select 3 as val, 'b' as var from dual union all
  4       select 4 as val, 'b' as var from dual union all
  5       select 5 as val, 'b' as var from dual union all
  6       select 6 as val, 'c' as var from dual union all
  7       select 7 as val, 'd' as var from dual union all
  8       select 8 as val, 'e' as var from dual union all
  9       select 9 as val, 'e' as var from dual union all
10       select 0 as val, 'f' as var from dual)
11   select *from t
12   where t.var = coalesce(:pvar1,:pvar2,:pvar3,:pvar4,t.var);
       VAL V
         3 b
         4 b
         5 b
Message was edited by:
        jeneesh
I did mistake. Follow Dave's post