62、图与递归查询技术解析

图与递归查询技术解析

1. 祖先查询

在实际应用中，查询给定节点的祖先（即路径）是常见需求，例如返回某个员工的管理链。要实现这一功能，可以使用以下代码创建 Managers 函数：

-- Function: Managers, Ancestors with optional level limit 
-- 
-- Input   : @empid INT : Employee id 
--           @maxlevels : Max number of levels to return  
-- 
-- Output  : @Mgrs Table: id and level of managers of 
--                        input employee in all levels <= @maxlevels 
-- 
-- Process : * In a loop, while current manager is not null 
--             and previous level is smaller than @maxlevels 
--             insert into @Mgrs current manager, 
--             and get next level manager 
--------------------------------------------------------------------- 
IF OBJECT_ID(N'dbo.Managers', N'TF') IS NO