Optimize rows to columns conversion - sql

Question

I have a big Oracle table (around 40 million rows) that looks like this:
ID Name Question Answer Reason
3 Name1 1 Yes blah blah
3 Name1 2 No NA
3 Name1 3 No NA
3 Name1 4 Yes blah2
3 Name1 5 Yes null
3 Name1 6 Yes blah3
3 Name1 7 No null
6 Name2 1 Yes blah4444
6 Name2 2 No null
6 Name2 3 Yes blah3
6 Name2 4 NA blah5
6 Name2 5 Yes null
6 Name2 6 Yes blah6
6 Name2 7 NA null
I need one row per ID i.e. I will need to add columns for each question's answer (there are 7 questions per ID) and each question's reason. I need to make it look like this:
ID Name Q1 Q1-Reason Q2 Q2-Reason Q3 Q3-Reason etc.
3 Name1 Yes blah blah No null
6 Name2 Yes blah4444 No null
My query currently looks like this:
select
A.ID,A.NAME,B1.Q1,B1.Q1-REASON,B2.Q2,B2.Q2-REASON
from
TABLENAME A
inner join
(
select distinct C1.ID,C1.ANSWER as Q1,C1.REASON as Q1-REASON
from TABLENAME C1
where C1.QUESTION=1
) B1 on B1.ID=A.ID
inner join
(
select distinct C2.ID,C2.ANSWER as Q2,C2.REASON as Q2-REASON
from TABLENAME C2
where C2.QUESTION=2
) B2 on B2.ID=A.ID
...
...
However, as the table is huge, this is taking a VERY long time to retrieve the data. Could someone suggest ways to optimize this query?
I'm on Oracle 10g and SQLDeveloper 4.0.2.15

Answer 1

You could do this:
SELECT
TABLENAME.ID,
TABLENAME.Name,
MAX(CASE WHEN TABLENAME.Question=1 THEN TABLENAME.Answer ELSE NULL END) AS Q1,
MAX(CASE WHEN TABLENAME.Question=1 THEN TABLENAME.Reason ELSE NULL END) AS Q1_Reason,
MAX(CASE WHEN TABLENAME.Question=2 THEN TABLENAME.Answer ELSE NULL END) AS Q2,
MAX(CASE WHEN TABLENAME.Question=2 THEN TABLENAME.Reason ELSE NULL END) AS Q2_Reason,
MAX(CASE WHEN TABLENAME.Question=3 THEN TABLENAME.Answer ELSE NULL END) AS Q3,
MAX(CASE WHEN TABLENAME.Question=3 THEN TABLENAME.Reason ELSE NULL END) AS Q3_Reason
/*And so on*/
FROM
TABLENAME
GROUP BY
TABLENAME.ID,
TABLENAME.Name