SQL Server HierarchyID：如何添加多个子级？

Question

Itzik Ben-Gan 在此描述了一些如何使用 HierarchyId 数据类型的简单方法。

http://sqlmag.com/t-sql/hierarchyid

他使用存储过程将子进程添加到某个根目录

-- Web Listing 2: Script to Create Stored Procedure usp_AddEmp
IF OBJECT_ID('dbo.usp_AddEmp', 'P') IS NOT NULL
  DROP PROC dbo.usp_AddEmp;
GO
CREATE PROC dbo.usp_AddEmp
  @empid   AS INT,
  @mgrid   AS INT = NULL,
  @empname AS VARCHAR(25),
  @salary  AS MONEY
AS

DECLARE
  @hid            AS HIERARCHYID,
  @mgr_hid        AS HIERARCHYID,
  @last_child_hid AS HIERARCHYID;

IF @mgrid IS NULL
  SET @hid = HIERARCHYID::GetRoot();
ELSE
BEGIN
  SET @mgr_hid = (SELECT hid FROM dbo.Employees WHERE empid = @mgrid);
  SET @last_child_hid =
    (SELECT MAX(hid) FROM dbo.Employees
     WHERE hid.GetAncestor(1) = @mgr_hid);
  SET @hid = @mgr_hid.GetDescendant(@last_child_hid, NULL);
END

INSERT INTO dbo.Employees(empid, hid, empname, salary)
  VALUES(@empid, @hid, @empname, @salary);
GO

要向树添加任何叶子，需要像这样调用此过程：

EXEC dbo.usp_AddEmp
  @empid =  1, @mgrid = NULL, @empname = 'David'  , @salary = $10000.00;
EXEC dbo.usp_AddEmp
  @empid =  2, @mgrid =    1, @empname = 'Eitan'  , @salary = $7000.00;
EXEC dbo.usp_AddEmp
  @empid =  3, @mgrid =    1, @empname = 'Ina'    , @salary = $7500.00;
EXEC dbo.usp_AddEmp
  @empid =  4, @mgrid =    2, @empname = 'Seraph' , @salary = $5000.00;
EXEC dbo.usp_AddEmp
  @empid =  5, @mgrid =    2, @empname = 'Jiru'   , @salary = $5500.00;
EXEC dbo.usp_AddEmp
  @empid =  6, @mgrid =    2, @empname = 'Steve'  , @salary = $4500.00;
EXEC dbo.usp_AddEmp
  @empid =  7, @mgrid =    3, @empname = 'Aaron'  , @salary = $5000.00;
EXEC dbo.usp_AddEmp
  @empid =  8, @mgrid =    5, @empname = 'Lilach' , @salary = $3500.00;
EXEC dbo.usp_AddEmp
  @empid =  9, @mgrid =    7, @empname = 'Rita'   , @salary = $3000.00;
EXEC dbo.usp_AddEmp
  @empid = 10, @mgrid =    5, @empname = 'Sean'   , @salary = $3000.00;
EXEC dbo.usp_AddEmp
  @empid = 11, @mgrid =    7, @empname = 'Gabriel', @salary = $3000.00;
EXEC dbo.usp_AddEmp
  @empid = 12, @mgrid =    9, @empname = 'Emilia' , @salary = $2000.00;
EXEC dbo.usp_AddEmp
  @empid = 13, @mgrid =    9, @empname = 'Michael', @salary = $2000.00;
EXEC dbo.usp_AddEmp
  @empid = 14, @mgrid =    9, @empname = 'Didi'   , @salary = $1500.00;

我的问题是：

我有一张表，其中包含叶子兄弟列表，我需要将其添加到同一级别的父级 14 中

declare @toadd table
 (
    empid   INT,
    mgrid   INT,
    empname VARCHAR(25),
    salary  MONEY
)

insert into @toadd(empid, mgrid, empname, salary)
select 15, 14, 'Itzik', $0.01
union all
select 16, 14, 'Jack', $0.02
union all
select 17, 14, 'Alex', $0.03
union all
select 18, 14, 'Mary', $0.04
union all
select 19, 14, 'John', $0.05

我可以创建游标并调用该过程 N 次。 但也许可以做得更有效？不知何故在一个查询中？

Answer 1

您可以使用“/[int/][…n]”形式的字符串将正确转换为 HierarchyId 的事实。因此，不要使用 GetDescendant 向经理添加下属，而是获取经理的 HierarchyId，对其调用 ToString()，在其上附加“{EmpId}/”，然后将其转换回 HierarchyId（或者如果具体来说：

列已经是这种类型。

with emps_and_mgrs as (
   select *, m.hid as mhid
   from @toadd as t
   cross apply (
      select hid
      from dbo.Employees
      where empid= t.mgrid
   ) as m
)

INSERT INTO dbo.Employees(empid, hid, empname, salary)
select empid, mhid.ToString() + cast(empid as varchar) + '/', empname, salary
from emps_and_mgrs;

这假设每个人的 hid 值的形式为“{manager's hid}/empid/”。这包括原始示例中的 David；他的值不是 GetRoot()（即“/”），而是“/1/”。另外值得注意的是，如果您打算采用此策略，我还将经理的 empid 存储在行中。这样，您可以编写一个递归 cte，仅使用 empid 和经理的 empid 在出现问题时重新生成所有 HierarchyId。