将 child 记录连接到 parent 并盛大 parents

Question

项目table中的每一项都有一个departmentID，每个部门id最多可以有3个grandparents。现在我需要显示每个项目及其部门和 parents.

我进行了 3 次简单的连接，结果成功了。

SELECT        tDepartment.id, tDepartment.Name, tDepartment_1.Name AS Parent1, tDepartment_2.Name AS Parent2, tDepartment_3.Name AS Parent3
FROM            tDepartment AS tDepartment_3 RIGHT OUTER JOIN
                         tDepartment LEFT OUTER JOIN
                         tDepartment AS tDepartment_1 ON tDepartment.ParentID = tDepartment_1.id LEFT OUTER JOIN
                         tDepartment AS tDepartment_2 ON tDepartment_1.ParentID = tDepartment_2.id ON tDepartment_3.id = tDepartment_2.ParentID
ORDER BY tDepartment.Name

我的问题是，是否可以通过使用 CTE 或任何其他想法以更简洁的方式完成？

Answer 1

为什么左右混用？

SELECT tDepartment.id, tDepartment.Name
      ,tDepartment_1.Name AS Parent1
      ,tDepartment_2.Name AS Parent2
      ,tDepartment_3.Name AS Parent3
  FROM tDepartment 
  LEFT OUTER JOIN tDepartment AS tDepartment_1 
       ON tDepartment.ParentID = tDepartment_1.id 
  LEFT OUTER JOIN tDepartment AS tDepartment_2 
    ON tDepartment_1.ParentID = tDepartment_2.id
  LEFT OUTER JOINtDepartment AS tDepartment_3                      
       ON tDepartment_3.id = tDepartment_2.ParentID
 ORDER BY tDepartment.Name

将 child 记录连接到 parent 并盛大 parents

Connect child record to parent and grand parents

tsql

sql-server

parent-child

sql-server-2014