Sqlite：自定义连接两个表？

Question

我有点遇到这个问题：我有一个sqlite数据库，其中包含两个使用公共ID连接的表。我想从两个表中检索数据，并填充一个新表格，表示＆＃39; table3＆＃39;列有＆＃39; category_id＆＃39;，＆＃39;问题＆＃39;，correct_answer＆＃39;，＆＃39; wrong_answer1＆＃39;，wrong_answer2＆＃39;，＆＃39; wrong_answer3＆＃39;。如何实现这一目标？请看下面的图片。

提前多多感谢！

Answer 1

假设您总是有一个正确答案和三个错误答案，您可以使用此查询：

       SELECT Q.category_id, 
              Q.value AS Question,
              RA.value AS CorrectAns,
              WA1.value AS WrongAns1,
              WA2.value AS WrongAns2,
              WA3.value AS WrongAns3
         FROM question Q
   INNER JOIN answer RA  ON (RA.question_id = Q.id  AND RA.isCorrect = 1)
   INNER JOIN answer WA1 ON (WA1.question_id = Q.id AND WA1.isCorrect = 0)
   INNER JOIN answer WA2 ON (WA2.question_id = Q.id AND WA2.isCorrect = 0)
   INNER JOIN answer WA3 ON (WA3.question_id = Q.id AND WA3.isCorrect = 0)
        WHERE WA1.id < WA2.`id`
          AND WA2.id < WA3.`id`
          AND Q.id = 102752

如果错误答案的数量不总是三，您可以使用其他查询。

       SELECT Q.category_id, 
              Q.value AS Question,
              RA.value AS CorrectAns,
              GROUP_CONCAT(WA.value) AS WrongAnswers
         FROM question Q
   INNER JOIN answer RA ON (RA.question_id = Q.id AND RA.isCorrect = 1)
    LEFT JOIN answer WA ON (WA.question_id = Q.id AND WA.isCorrect = 0)
        WHERE Q.id = 102752

请注意，在这种情况下，所有错误的答案都会在同一列中返回。