表列合并查询

Question

我做了一张桌子 查询是

CREATE TABLE questions (
     _id             INTEGER PRIMARY KEY AUTOINCREMENT
   , question        TEXT
   , correct_answer  TEXT    DEFAULT (null)
   , answer1         TEXT    DEFAULT (null)
   , answer2         TEXT    DEFAULT (null) 
   , answer3         TEXT    DEFAULT (null)
   , answer4         TEXT    DEFAULT (null)
   , difficulty      INTEGER DEFAULT (null) 
   , nid             INTEGER
);

现在要省略correct_answer列，并在answer1列中做出正确答案，在answer2，answer3，answer4中做出其他3个错误答案。 但问题是目前正确答案可能是四个中的任何一个，所以我无法合并

作为示例表就像

你可以在第一行看到答案2中的正确答案，第二行正确答案是在答案4中

那我怎么只在answer1栏中给出正确答案，在答案2，答案3，答题4中分别给出其他错误答案？

什么是sql查询？或任何其他想法？

Answer 1

我会做这样的事情：

insert into question_new (_id, qestion, answer1, answer2, answer3, answer4)
SELECT _id, question, 
correct_answer as answer1, 
if (correct_answer = answer2 , answer1 , answer2) as answer2,
if (correct_answer = answer3 , answer1 , answer3) as answer3,
if (correct_answer = answer4 , answer1 , answer4) as answer4
 FROM questions

简单来说：

1. answer1将始终是correct_answer列。
2. answer2 / 3/4将是
   • 如果与正确答案不同（与默认表格相同），则为同一列
   • 答案1如果等于正确答案（在答题1中有正确答案，所以你需要在新位置设置错误的答案1）

<强>更新

使用case when

添加了相同的查询

insert into question_new (_id, qestion, answer1, answer2, answer3, answer4)
SELECT _id, question, 
correct_answer as answer1, 
case when correct_answer = answer2 then answer1 else answer2 end as answer2,
case when correct_answer = answer3 then answer1 else answer3 end as answer3,
case when correct_answer = answer4 then answer1  else answer4 end as answer4
 FROM questions

Answer 2

我会这样做

insert into questions2(_id, qestion, answer1, answer2, answer3, answer4)
select _id, question , correct_answer as answer1,
case when correct_answer = answer1 then answer2 else answer1 end answer2,
case when correct_answer = answer2 then answer3 else answer2 end answer3,
case when correct_answer = answer3 then answer4 else answer3 end answer4
from questions

因此，您最终会得到新表格，其中包含您所需格式的问题

Answer 3

你可以试试这个 -

SELECT question, correct_answer,
CASE WHEN answer1 != correct_answer THEN answer1 ELSE answer2 END AS incorrect1,
CASE WHEN (answer1 != correct_answer AND answer2 != correct_answer) THEN answer2 ELSE answer3 END AS incorrect2,
CASE WHEN (answer1 != correct_answer AND answer2 != correct_answer AND answer3 != correct_answer) THEN answer3 ELSE answer4 END AS incorrect3
FROM questions

Answer 4

有点晚了，但你可以更新你的表而不需要辅助表来存储你想要的数据

UPDATE questions

SET 
answer2 = CASE WHEN answer2 = correct_answer
          THEN answer1 ELSE answer2 END,

answer3 = CASE WHEN answer3 = correct_answer
          THEN answer1 ELSE answer3 END,

answer4 = CASE WHEN answer4 = correct_answer
          THEN answer1 ELSE answer4 END,
answer1 = correct_answer

CHECK 的 SQL FIDDLE HERE