Problem using Decode/Case

Question

I have one table which stores candidates' response. The structure is like this
(Seatno, Questionnumber, Answer).
And I have another table Master as (Questionnumber, Answer)
Now I want to calculate marks by comparing Candidate's response with Master.
I tried to use decode and case. But was not successful.
My query with decode was ...
select c1.candidatesrno, sum(decode(c1.answer,(c1.answer=m1.answer),1,0))
from candidate c1,master q1
where c1.question=m1.question
group by c1.candidatesrno
And query with CASE was...
select c1.candidatesrno,
case when (c1.answer=m1.answer) then 1 else 0
end resultset
from candidate c1,master m1
where c1.questionnumber=m1.questionnumber
group by c1.candidatesrno
Can anybody help ?

Answer 1

I want to compare candidate's response with master
table.
Now for each question of Candidate, if its answer
matches with answer in Master table I have to give 1
marks...if it does not match I have to give 0
marks...like this there are two-three conditions...
Something like this ?
test@ORA10G>
test@ORA10G> with master as (
  2    select 'Q1' as question_num, 'A1' as answer_num from dual union all
  3    select 'Q2', 'A2' from dual union all
  4    select 'Q3', 'A3' from dual),
  5  candidate_response as (
  6    select 'S1' as seat_num, 'Q1' as question_num, 'A1' as answer_num from dual union all
  7    select 'S1', 'Q2', 'A2' from dual union all
  8    select 'S1', 'Q3', 'A3' from dual union all
  9    select 'S2', 'Q1', 'A5' from dual union all
10    select 'S2', 'Q2', 'A6' from dual union all
11    select 'S2', 'Q3', 'A3' from dual)
12  --
13  select
14    cr.seat_num,
15    cr.question_num,
16    cr.answer_num,
17    case when m.question_num is null and m.answer_num is null then '0 point'
18         else '1 point'
19    end as points
20  from candidate_response cr, master m
21  where cr.question_num = m.question_num(+)
22  and cr.answer_num = m.answer_num(+)
23  order by cr.seat_num, cr.question_num, cr.answer_num;
SE QU AN POINTS
S1 Q1 A1 1 point
S1 Q2 A2 1 point
S1 Q3 A3 1 point
S2 Q1 A5 0 point
S2 Q2 A6 0 point
S2 Q3 A3 1 point
6 rows selected.
test@ORA10G>
test@ORA10G> with master as (
  2    select 'Q1' as question_num, 'A1' as answer_num from dual union all
  3    select 'Q2', 'A2' from dual union all
  4    select 'Q3', 'A3' from dual),
  5  candidate_response as (
  6    select 'S1' as seat_num, 'Q1' as question_num, 'A1' as answer_num from dual union all
  7    select 'S1', 'Q2', 'A2' from dual union all
  8    select 'S1', 'Q3', 'A3' from dual union all
  9    select 'S2', 'Q1', 'A5' from dual union all
10    select 'S2', 'Q2', 'A6' from dual union all
11    select 'S2', 'Q3', 'A3' from dual)
12  --
13  select cr.seat_num, count(*) as score
14  from candidate_response cr, master m
15  where cr.question_num = m.question_num
16  and cr.answer_num = m.answer_num
17  group by cr.seat_num
18  order by cr.seat_num;
SE      SCORE
S1          3
S2          1
test@ORA10G>
test@ORA10G>pratz