sql-server - 在层次结构中查找元素

Question

我正在尝试使用WITHT-SQL 创建分层查询。我想做的是，例如，直接或间接地确定 John 是否是 Ryan 的老板？

我该如何为此编写查询？

Answer 1

WITH BossOf AS(
   SELECT bossId, Id From Employees
       UNION ALL
   SELECT b.bossId, e.Id 
   FROM Employees AS e
   INNER JOIN BossOf b ON b.Id = e.bossId
)
SELECT * FROM BossOf
   WHERE Id = 'Ryan'

就像你可以用 BossOf 做的一个例子......

WITH BossOf AS(
   SELECT bossId, Id From Employees
       UNION ALL
   SELECT b.bossId, e.Id 
   FROM Employees AS e
   INNER JOIN BossOf b ON b.Id = e.bossId
)
SELECT * FROM Employees
    WHERE Id IN (SELECT BossId 
                    FROM BossOf
                    Where Id = 'Ryan')

甚至

WITH BossOf AS(
   SELECT bossId, Id From Employees
       UNION ALL
   SELECT b.bossId, e.Id 
   FROM Employees AS e
   INNER JOIN BossOf b ON b.Id = e.bossId
)
SELECT COUNT(*) FROM BossOf
   WHERE Id = 'Ryan'
   AND BossId = 'John'