mysql - 如何在同一张表上查询不同的where条件和连接结果

Question

我有表格questionbank，我想根据不同的where条件提取问题，例如

(SELECT unit, Subject, Question, OptionA, OptionB, OptionC, OptionD , CorrectAnswer, marks 
FROM questionbank 
WHERE  Department = "DCP" 
and Subject = "CO" 
and Unit = "1" 
and marks = "1" LIMIT 3) 
UNION (SELECT unit,Subject,Question,OptionA ,OptionB ,OptionC ,OptionD ,CorrectAnswer,marks
FROM questionbank 
WHERE  Department ="DCP"  
and Subject="CO" 
and Unit="1" 
and marks ="2" LIMIT 1 )

我有 6 个单元，标记为 1、2、3 或 4。并且限制由用户指定。这将是传统联合方式中安静的大查询。如何以简单易行的方式做到这一点？

只有 unit (1to6) , marks (1to4) 和 limit 在此查询中是可变的。

Answer 1

你的要求一点都不清楚，但是你可以在你的where中用or组合不同的可能条件，比如

SELECT  unit, Subject, Question, OptionA, OptionB, OptionC, OptionD , CorrectAnswer, marks 
FROM    questionbank 
WHERE   Department = "DCP" and Subject = "CO" and (
          (Unit = "1" and marks = "1") OR
          (Unit = "2" and marks = "3") OR
          /* ... */
          (Unit = "6" and marks = "4")
        )
LIMIT 3