查询以获取具有或不具有组concat的多行

Question

I have the following table structure:

 users:
    id PK
    username
    email
    salt
    password
    date_created

questions:
    id PK
    user_id FK(users)
    title
    date_created
    date_updated

answers:
    id PK
    question_id FK(questions)
    user_id FK(users)
    body
    date_created

So I need a query that gets data from these tables and displays the user's last 5 questions and for each question the first 3 answers. Something like this:

"What is my favorite color? posted by user

red - posted by user1
green - posted by user2
yellow - posted by user3

.....
"

So this is the display I am aiming for. How can I do this in 1 query? Should I use group concat to group the multiple answers for 1 question? Or should I get the results and parse the array in PHP to group the answers by question_id. Also I need this query to be very fast. I am not sure if it will be faster making 1 query or making multiple queries that get the user questions and after that the question answers.

Answer 1

I think the key "hint" I would give is that you can use regular CONCAT() inside of GROUP_CONCAT(); and then use JOINs and perhaps some of the techniques mentioned in the comments to get you the intermediate result-set that those two functions need to get you your output.