Flatten a response to an SQL query - mysql

Question

I am trying to get a flat table for a question and answer table with mysql. This are my tables.
PollQuestion
PollID | Question| A | B | C | D | E | TimeStamp
PollReponse
PollReponseID | PollID | UserID | Answer
In the PollAnswer table I get Five answers as VARCHAR A, B, C, D, E.
I have written a query to group the answers by A, B, C, D, E.
select q.Question
, q.PollID
, r.Answer
, count(r.Answer)
from pollQuestions q
, pollResponse r
where q.PollID = r.PollID
group
by r.Answer
, q.Question
, q.PollID
order
by r.PollID;
Which gives me a response as follows.
Question | PollID | Answer | count
alpha | 1 | A | 2
alpha | 1 | B | 3
alpha | 1 | C | 4
alpha | 1 | D | 0
alpha | 1 | E | 0
betas | 2 | A | 3
betas | 2 | B | 4
betas | 2 | C | 4
betas | 2 | D | 6
betas | 2 | E | 0
I want to flatten the answer like this.
Question | PollID | countA | countB | countC | countD | countE
alpha | 1 | 2 | 2 | 4 | 0 | 0
betas | 2 | 3 | 4 | 4 | 6 | 0
Is there anyway I can achieve this without changing the table structure?
Any pointer would be appreciated.

Answer 1

You can try to use condition aggregate function.
select
pollQuestions.Question,
pollQuestions.PollID,
count(CASE WHEN pollResponse.Answer ='A' THEN 1 END) countA,
count(CASE WHEN pollResponse.Answer ='B' THEN 1 END) countB,
count(CASE WHEN pollResponse.Answer ='C' THEN 1 END) countC,
count(CASE WHEN pollResponse.Answer ='D' THEN 1 END) countD,
count(CASE WHEN pollResponse.Answer ='E' THEN 1 END) countE
from pollQuestions
JOIN pollResponse on pollQuestions.PollID = pollResponse.PollID
group by
pollQuestions.Question,
pollQuestions.PollID
order by
pollResponse.PollID;
NOTE
I would use JOIN instead of comma , because JOIN syntax is clearer than , about connect two tabls.

Answer 2

You can use group by with sum(case when...) like below:
select pq.Question, pq.PollID,
sum(case when pr.Answer = 'A' then 1 else 0 end) as 'countA',
sum(case when pr.Answer = 'B' then 1 else 0 end) as 'countB',
sum(case when pr.Answer = 'C' then 1 else 0 end) as 'countC',
sum(case when pr.Answer = 'D' then 1 else 0 end) as 'countD',
sum(case when pr.Answer = 'E' then 1 else 0 end) as 'countE'
from PollQuestion pq
left join PollResponse pr on pq.PollID = pr.PollID
group by pq.Question, pq.PollID