Mysql选择一些随机行和一个特定行

Question

I have a quiz system which questions have multiple choises.

I want to show the right answer plus four more wrong choices. Totally I must have five choices.

Table choices

id | choice | questionid | correct
---+--------+------------+--------
 1 | choice1|          1 |   false
 2 | choice2|          1 |   false
 3 | choice3|          1 |   false
 4 | choice4|          1 |   false
 5 | choice5|          1 |    true
 6 | choice6|          1 |   false
 7 | choice7|          1 |   false
 8 | choice8|          1 |   false

Table may be extended...

Now I want to select four wrong answers and the correct answer to list below the question. And for each user sees the question choices should be different.

How can I query the table for this result? I do not want to make two queries and bind them in an array like below:

SELECT   * 
FROM     `choices` 
WHERE    questionid = :qid AND correct = true

SELECT   * 
FROM `choices` 
WHERE questionid = :qid AND 
      correct = false AND 
      id IN( 
             SELECT  id 
             FROM    `choices` 
             ORDER BY RAND() 
             LIMIT 4
            )

Instead it should be done with one step I guess.

Answer 1

SELECT *
FROM `choises`
WHERE questionid = :qid
ORDER BY correct DESC, RAND()
LIMIT 5

Assuming correct is some sort of int. Otherwise you might need to change DESC to ASC .

You can 'shuffle' the 5 results using one more ORDER BY RAND() like this:

SELECT * FROM (
    SELECT *
    FROM `choises`
    WHERE questionid = :qid
    ORDER BY correct DESC, RAND()
    LIMIT 5
) as t
ORDER BY RAND()