TSQL 递归更新？

Question

我想知道 tsql (CTE) 中是否存在递归更新

ID  parentID value
--  -------- -----
1   NULL     0
2   1        0
3   2        0
4   3        0
5   4        0
6   5        0

我可以使用例如 CTE 从 ID = 6 递归更新列 value 到最顶行吗？

Answer 1

是的，应该是。 MSDN gives an example:

USE AdventureWorks;
GO
WITH DirectReports(EmployeeID, NewVacationHours, EmployeeLevel)
AS
(SELECT e.EmployeeID, e.VacationHours, 1
  FROM HumanResources.Employee AS e
  WHERE e.ManagerID = 12
  UNION ALL
  SELECT e.EmployeeID, e.VacationHours, EmployeeLevel + 1
  FROM HumanResources.Employee as e
  JOIN DirectReports AS d ON e.ManagerID = d.EmployeeID
)
UPDATE HumanResources.Employee
SET VacationHours = VacationHours * 1.25
FROM HumanResources.Employee AS e
JOIN DirectReports AS d ON e.EmployeeID = d.EmployeeID;