DECLARE @i int = 4 

DECLARE @i INT=2
SELECT TOP 3 @i*=@i FROM sys.objects
SELECT @i 

SELECT Country,TitleOfCourtesy,COUNT(EmployeeID) 汇总结果 FROM Employees 
GROUP BY Grouping Sets(Country,TitleOfCourtesy,(Country,TitleOfCourtesy))
Order By Country DESC,TitleOfCourtesy 

CREATE TABLE tbSource(C1 INT PRIMARY KEY,C2 NVARCHAR(10))
GO
INSERT tbSource VALUES(1,N'甲'),(2,N'乙')
GO
SELECT * INTO tbDest FROM tbSource 

DELETE tbSource WHERE c1=1
UPDATE tbSource SET c2=N'乙2' WHERE C1=2
INSERT tbSource VALUES(3,N'丙') 

MERGE tbDest D
  USING tbSource s
  ON D.c1 = S.c1
  WHEN MATCHED THEN --修改
    UPDATE SET D.c2 = S.c2
  WHEN SOURCE NOT MATCHED THEN  --删除
     DELETE
  WHEN TARGET NOT MATCHED THEN  --新增
    INSERT VALUES(c1, c2)
    OUTPUT $action, INSERTED.c1 [New c1], 
                    INSERTED.c2 [New c2], 
                    DELETED.c1  [Original c1],
                    DELETED.c2  [Original c2]; 

-- Step 1: 建立有阶层特征的数据表
--         HierarchyID 可比较，因此可当作主键
CREATE TABLE tbEmployee
(
   OrgNode HierarchyID PRIMARY KEY CLUSTERED,
   OrgLevel AS OrgNode.GetLevel(),
   EmployeeID int UNIQUE NOT NULL,
   EmpName nvarchar(20) NOT NULL) ;
GO 

-- Step 2: 建立 breadth-first 索引，也就是相同父亲的数据放在一起
--         以数值 OrgLevel 放在前面，然后才是结点
CREATE UNIQUE INDEX EmployeeOrgNc1 
ON tbEmployee(OrgLevel, OrgNode) ;
GO 

-- Step 3: 加载数据
-- 载入根结点
INSERT tbEmployee(OrgNode, EmployeeID, EmpName)
VALUES (hierarchyid::GetRoot(), 1, N'甲') ;
GO 

SELECT OrgNode.ToString() [文字描述阶层], 
OrgNode, OrgLevel, EmployeeID, EmpName
FROM tbEmployee ;

--透过 GetDescendant 函数建立第一个子结点
DECLARE @Manager hierarchyid 
SET @Manager = (SELECT OrgNode FROM tbEmployee WHERE EmployeeID = 1) 

--加入子结点，因为是第一个子结点，所以不需要算位置
INSERT tbEmployee (OrgNode, EmployeeID, EmpName)
VALUES
(@Manager.GetDescendant(NULL, NULL), 12, N'乙') ; 
GO 

SELECT OrgNode.ToString() AS  [文字描述阶层], 
OrgNode, OrgLevel, EmployeeID, EmpName 
FROM tbEmployee ;

-- Step 4: 建立新增节点的共享预存程序
CREATE PROC AddEmp(@mgrid int, @empid int, @e_name nvarchar(20)) 
AS 
BEGIN
   -- mOrgNode 父节点
   -- lc 该父节点的最后一个子结点
   DECLARE @mOrgNode hierarchyid, @lc hierarchyid
   SELECT @mOrgNode = OrgNode 
   FROM tbEmployee 
   WHERE EmployeeID = @mgrid 

   SET TRANSACTION ISOLATION LEVEL SERIALIZABLE
   BEGIN TRANSACTION
      SELECT @lc = max(OrgNode) 
      FROM tbEmployee 
      WHERE OrgNode.GetAncestor(1) =@mOrgNode ; --传回上一阶，相同父节点的最大子结点 

      INSERT tbEmployee(OrgNode, EmployeeID, EmpName)
      VALUES(@mOrgNode.GetDescendant(@lc, NULL), @empid, @e_name) --将新增节点加在父节点最大的孩子旁
   COMMIT
END ;
GO 

EXEC AddEmp 12, 121, N'丙';
EXEC AddEmp 12, 122, N'丁';
EXEC AddEmp 1, 13, N'戊';
EXEC AddEmp 121, 1211, N'己';
EXEC AddEmp 13, 131, N'庚';
GO 

SELECT OrgNode.ToString() AS  [文字描述阶层], 
OrgNode, OrgLevel, EmployeeID, SPACE(OrgNode.GetLevel()*5) + EmpName
FROM tbEmployee;