将 RIGHT 外连接转换为左外连接 SQLite

我需要为 Sqlite 设计一个查询 原来的查询是这样的

 FROM            PhysicianActivity INNER JOIN
                     Activity ON PhysicianActivity.ActivityID = Activity.ID RIGHT OUTER JOIN
                     PhysicianFrequency ON PhysicianActivity.PhysicianID = PhysicianFrequency.PhysicianID AND Activity.LegalEntityID = PhysicianFrequency.LegalEntityID 

知道 sqlite 不支持 RIGHT OUTER JOIN 所以我坚持使用 LEFT OUTER JOIN 但我无法将此查询转换为 LEFT OUTER JOIN

有人可以帮忙吗？

大多数人更喜欢LEFT OUTER JOIN。在大多数情况下，以下内容是等效的：

FROM  PhysicianFrequency LEFT JOIN
      PhysicianActivity 
      ON PhysicianActivity.PhysicianID = PhysicianFrequency.PhysicianID LEFT JOIN
      Activity
      ON PhysicianActivity.ActivityID = Activity.ID AND
         Activity.LegalEntityID = PhysicianFrequency.LegalEntityID 

我建议您使用表别名，以便查询更易于编写和阅读：

FROM  PhysicianFrequency pf LEFT JOIN
      PhysicianActivity pa
      ON pa.PhysicianID = pf.PhysicianID LEFT JOIN
      Activity a
      ON pa.ActivityID = a.ID AND
         a.LegalEntityID = pf.LegalEntityID