Question

我有一个测验系统，问题有多个选择。

我想表明正确的答案加上四个错误的选择。我必须有五个选择。

表格选择

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

表格可能会延长......

现在我想选择四个错误答案，并在问题下方列出正确答案。并且对于每个用户来说，问题选择应该是不同的。

如何在表格中查询此结果？我不想做两个查询并将它们绑定在如下数组中：

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
            )

相反，我应该一步完成。

Answer 1

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

假设correct是某种int。否则，您可能需要将DESC更改为ASC。

您可以使用另外一个ORDER BY RAND()来“混乱”5个结果：

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

Mysql选择一些随机行和一个特定行

1 个答案: