Question

我有一个只会产生2行的查询。每行包含一个问题及其匹配答案。我想要做的是有一行4列。如何才能做到这一点？我可以将值连接成一个字符串，但我宁愿不这样做。

有人能为我提供一个例子吗？这就是我所追求的：

Q1              A1            Q2                 A2 
Some question   Some answer   Another question   Another answer

这是我的查询

SELECT question, answer FROM
user_question AS uq
Join question AS q ON q.question_id = uq.question_id

Answer 1

当然可以，您只需要查询同一个表两次。您应该使用AS关键字，这样您就可以确定在SELECT和WHERE部分中使用了哪个版本的表：

SELECT a.question as q1,
       a.answer as a1,
       b.question as q2,
       b.answer as a2
FROM   user_question as a,
       user_question as b
WHERE  a.question_id = 1001
AND    b.question_id = 1002;

Answer 2

如何使用UNION？

像这样：

SELECT iQuestion, iAnswer
FROM
    (SELECT Q1 as iQuestion, -- change to orig column name
            A1 as iAnswer,   -- change to orig column name
            questionID
    FROM    user_question INNER JOIN question
                ON user_question.question_id = question.question_id
    UNION
    SELECT  Q2 as iQuestion, -- change to orig column name
            A2 as iAnswer,   -- change to orig column name
            questionID
    FROM    user_question INNER JOIN question
                ON user_question.question_id = question.question_id) as iResult
WHERE   iResult = 'QUESTIONID HERE'

PS：请发布您的表格的SCHEMA，以便我们知道确切的列名称以及您将在WHERE条件中使用的字段。

如何将2行的结果合二为一

2 个答案: