关于视图的从句不按联接顺序出现

Question

在SSMS 2012中，我将看到在MS中创建的一个大视图。当我将视图脚本到查询窗口时，FROM子句如下所示：

FROM         dbo.oa_projecttask_type RIGHT OUTER JOIN
    dbo.oa_project_task RIGHT OUTER JOIN
    dbo.[Functional Area] RIGHT OUTER JOIN
    dbo.oa_category ON dbo.[Functional Area].[Product Code] = dbo.oa_category.name RIGHT OUTER JOIN
    dbo.oa_project RIGHT OUTER JOIN
    dbo.vw_People_All_Ever RIGHT OUTER JOIN
    dbo.oa_task ON dbo.vw_People_All_Ever.[User ID] = dbo.oa_task.user_id ON dbo.oa_project.id = dbo.oa_task.project_id ON 
    dbo.oa_category.id = dbo.oa_task.category_id ON dbo.oa_project_task.id = dbo.oa_task.project_task_id ON 
    dbo.oa_projecttask_type.id = dbo.oa_task.projecttask_type_id LEFT OUTER JOIN
    dbo.upl_approval_status RIGHT OUTER JOIN
    dbo.oa_timesheet ON dbo.upl_approval_status.Code = dbo.oa_timesheet.status ON dbo.oa_task.timesheet_id = dbo.oa_timesheet.id
WHERE     (CONVERT(datetime, oa_task.created) > GETDATE() - 366) AND (oa_task.deleted IS NULL)

当我格式化子句以使联接和ON's位于单独的行时，它看起来如下所示：

FROM oa_projecttask_type 
   RIGHT OUTER JOIN oa_project_task 
   RIGHT OUTER JOIN [Functional Area] 
   RIGHT OUTER JOIN oa_category 
      ON [Functional Area].[Product Code] = oa_category.name 
   RIGHT OUTER JOIN oa_project 
   RIGHT OUTER JOIN vw_People_All_Ever 
   RIGHT OUTER JOIN oa_task 
      ON vw_People_All_Ever.[User ID] = oa_task.user_id 
      ON oa_project.id = oa_task.project_id 
      ON oa_category.id = oa_task.category_id 
      ON oa_project_task.id = oa_task.project_task_id 
      ON oa_projecttask_type.id = oa_task.projecttask_type_id 
   LEFT OUTER JOIN upl_approval_status 
   RIGHT OUTER JOIN oa_timesheet 
      ON upl_approval_status.Code = oa_timesheet.status 
      ON oa_task.timesheet_id = oa_timesheet.id
WHERE     (CONVERT(datetime, oa_task.created) > GETDATE() - 366) AND (oa_task.deleted IS NULL)

许多联接没有ON语句，但是视图编译和返回数据时没有错误。没有ON子句的右外联接意味着什么--它是笛卡儿连接吗？

更新:基于这个问题-- Wierd SQL Server view definition --以及它的链接，我们不能简单地将联接/ONs重新排列成更合理的顺序--顺序会影响检索的逻辑。我将用更容易理解的逻辑重写这个查询。感谢马汀史密斯和所有的人！

Answer 1

如果你再检查一遍，你会发现每个Right Outer Join都有他的ON语句，只是没有。

我猜所有joins都会找到自己的ON，因为ON语句是RIGHT/LEFT Outer Join正常工作所必需的。

有关这个主题的更多信息，您可以找到HERE，正如Martin Smith在评论中所写的。