mysql - 基于单元格值的动态列选择

Question

我有一个形状的问题数据库

ID , Question , Answer1 , Answer2 , Answer3 , Answer4 , True

其中“True”是正确答案的索引:

True = 0 --> Answer1
....
True = 3 --> Answer4

我只需要选择问题和正确答案，这是我目前得到的结果:

SELECT Question , 'Answer' || (True+1) From Questions

但它会返回问题和“answer1”或“answer2”...即:我不需要的列的名称是值

Answer 1

您可以在 MySQL 中使用 CASE。

SELECT  Question,
        CASE True
            WHEN 0 THEN Answer1
            WHEN 1 THEN Answer2
            WHEN 2 THEN Answer3
            WHEN 3 THEN Answer4
        END AS Answer
FROM    tableName

或

SELECT  Question,
        CASE 
            WHEN TRUE = 0 THEN Answer1
            WHEN TRUE = 1 THEN Answer2
            WHEN TRUE = 2 THEN Answer3
            WHEN TRUE = 3 THEN Answer4
        END AS Answer
FROM    tableName