MySQL single insert using subquery rows as columns - php

Question

How would I select 3 question IDs and use them as column data in for a single insert statement, using only MySQL.
I currently use the following statement to insert a new row into the game table by selecting a single random entry from the question table:
Current Table:
-------------------------------
| game | user_id | question_id |
-------------------------------
| 1 | 1 | 10 |
Current Statement:
INSERT INTO game (user_id, question_id)
SELECT u.id as user_id, q.id as question_id
FROM user u, question q
WHERE u.id =:uid
AND q.category = :category
ORDER BY RAND()
LIMIT 1
Game table:
I have added the columns opt_1-3 to allow for multiple choice
-------------------------------------------------------
| game | user_id | question_id | opt_1 | opt_2 | opt_3 |
-------------------------------------------------------
| 1 | 1 | 10 | 5 | 12 | 80 |
^ ^ ^
alternative wrong answers
I can achieve this with PHP, iterating over results and using two queries.
SELECT id FROM question
WHERE category = :category
ORDER BY RAND()
LIMIT 3
$opts = array();
foreach($result as $r){
$opts[] = $r->id;
}
INSERT INTO game (user_id, question_id)
SELECT u.id as user_id, q.id as question_id,
// add the following line to the query posted previously
$opt[0] AS opt_1, $opt[1] AS opt_2, $opt[2] AS opt_3
...
I want to know if its possible to achieve the same result purely using MySQL.

Answer 1

Not tested this much but this might do the job as the select for you.
Note that an order by rand() is not quick, and this involves a couple of cross joins which will also likely be slow if there are a large number of questions.
SELECT u.id as user_id, Sub1.aid, Sub1.bid, Sub1.cid
FROM user u,
(SELECT a.id AS aid, b.id AS bid, c.id AS cid
FROM question a, question b, question c
WHERE a.category = :category
AND a.category = :category
AND a.category = :category
AND a.id != b.id
AND a.id != c.id
AND b.id != c.id
ORDER BY RAND()
LIMIT 1) Sub1
WHERE u.id =:uid