在MySQL中为列创建排名变量

Question

我需要创建一个排名变量，它基本上是一个计数器。查询被写入获取UserId，ExamId。对于每个userid，可能会有多个exams，我需要创建一个新的列来获取考试索引。对于例如：在下面提到表

UserId ExamId CounterVariable 

2  3  2-1 
2  4  2-2 
3  5  3-1 
3  6  3-2 

---

SQL：

select us.grade as Grade,k.keyword as QuestionCategory,us.userid as UserId,ue.userExamId as ExamId,ue.completed as ExamCompletedDate,us.userSectionId as UserSectionId,qs.questionSectionId as QuestionSectionId, 
    coalesce(a13.answerId, a14.answerId, a15.answerId, a16.answerId) as AnswerId, 
    coalesce(a13.answer, a14.answer, a15.answer, a16.answer) as Answer, 
    coalesce(a13.correct, a14.correct, a15.correct, a16.correct) as Correct, 
    coalesce(a13.flagged, a14.flagged, a15.flagged, a16.flagged) as Flagged, 
    coalesce(a13.duration, a14.duration, a15.duration, a16.duration) as Duration, 
    coalesce(a13.blank, a14.blank, a15.blank, a16.blank) as Blank 
    from userSections us 
    join questionSections qs on qs.sectionId = us.sectionId 
    join questions q on q.questionId = qs.questionId 
    join keywords k on q.keywordId = k.keywordId 
    JOIN userExams ue ON ue.userExamId = us.userExamId 
    left join 
    isee_answers_2013.answers a13 on us.userSectionId = a13.userSectionId and qs.questionSectionId = a13.questionSectionId 
    left join 
    isee_answers_2014.answers a14 on us.userSectionId = a14.userSectionId and qs.questionSectionId = a14.questionSectionId 
    left join 
    isee_answers_2015.answers a15 on us.userSectionId = a15.userSectionId and qs.questionSectionId = a15.questionSectionId 
    left join 
    isee_answers_2016.answers a16 on us.userSectionId = a16.userSectionId and qs.questionSectionId = a16.questionSectionId 
WHERE 
    us.valid=1 and us.userid=56 
    order by us.grade,k.keyword,us.userid,ue.userExamId,us.userSectionId,qs.questionSectionId 

Answer 1

我猜你需要包括您发布的查询排名列。

在这种情况下，可使用以下：

SELECT rank, CONCAT(UserId, '-', rank) as CounterVariable, Grade, QuestionCategory, UserId, ExamId, ExamCompletedDate, UserSectionId, 
     QuestionSectionId, AnswerId, Answer, Correct, Flagged, Duration, Blank 
    FROM (SELECT @rn:=CASE WHEN @rn <> us.userid THEN 1 ELSE @rn+1 END AS rank, 
       @usr:=us.userid as usr, 
       us.grade as Grade, k.keyword as QuestionCategory, us.userid as UserId, 
       ue.userExamId as ExamId, ue.completed as ExamCompletedDate, us.userSectionId as UserSectionId, 
       qs.questionSectionId as QuestionSectionId, 
       coalesce(a13.answerId, a14.answerId, a15.answerId, a16.answerId) as AnswerId, 
       coalesce(a13.answer, a14.answer, a15.answer, a16.answer) as Answer, 
       coalesce(a13.correct, a14.correct, a15.correct, a16.correct) as Correct, 
       coalesce(a13.flagged, a14.flagged, a15.flagged, a16.flagged) as Flagged, 
       coalesce(a13.duration, a14.duration, a15.duration, a16.duration) as Duration, 
       coalesce(a13.blank, a14.blank, a15.blank, a16.blank) as Blank 
      FROM userSections us 
      join questionSections qs on qs.sectionId = us.sectionId 
      join questions q on q.questionId = qs.questionId 
      join keywords k on q.keywordId = k.keywordId 
      JOIN userExams ue ON ue.userExamId = us.userExamId 
      left join 
    isee_answers_2013.answers a13 on us.userSectionId = a13.userSectionId and qs.questionSectionId = a13.questionSectionId 
      left join 
    isee_answers_2014.answers a14 on us.userSectionId = a14.userSectionId and qs.questionSectionId = a14.questionSectionId 
      left join 
    isee_answers_2015.answers a15 on us.userSectionId = a15.userSectionId and qs.questionSectionId = a15.questionSectionId 
      left join 
    isee_answers_2016.answers a16 on us.userSectionId = a16.userSectionId and qs.questionSectionId = a16.questionSectionId 
      join (SELECT @rn:=0) t1 
      join (SELECT @usr=0) t2 
     WHERE us.valid=1 and us.userid=56 
     ORDER BY us.grade,k.keyword,us.userid,ue.userExamId,us.userSectionId,qs.questionSectionId 
     ) AS tab;