用JOIN/APPLY替換子查詢

Question

我有以下SQL。

SELECT t0.QustionId, t1.QuestionText, t2.AnswerText FROM 
ActiveQuestion AS t0 
INNER JOIN Question AS t1 
    ON t1.QuestionId = ActiveQuestion.QuestionId 
LEFT OUTER JOIN Answer AS t2 
    ON t2.SectionId = t0.SectionId 
    AND t1.ParentId IN 
      (SELECT QuestionId 
        FROM Question WHERE SharedQuestionId = t2.SharedQeustionId) 

問題可以共享（具有相同的SharedQuestionId），問題可以有父問題。

我想擺脫子查詢。什麼是正確的方法來做到這一點？

Answer 1

JOIN表Question一個更多的時間用不同的別名：

SELECT 
    t0.QustionId, 
    t1.QuestionText, 
    t2.AnswerText, 
    p.questionI ParentQuestionId 
FROM ActiveQuestion  AS t0 
INNER JOIN Question  AS t1 ON t1.QuestionId  = ActiveQuestion.QuestionId 
LEFT OUTER JOIN Answer AS t2 ON t2.SectionId  = t0.SectionId 
LEFT OUTER JOIN Question AS p ON t1.ParentId  = p.QuestionId 
           AND p.SharedQuestionId = t2.SharedQeustionId;