在層次結構中查找元素

Question

我試圖使用T-SQL的WITH創建分層查詢。例如，我想要做的是直接或間接地發現約翰是瑞安的老闆嗎？

如何爲此編寫查詢？

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' 

正如你可以BossOf做一個例子...

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'