Remaping keys with sequential update

CREATE TABLE Product(
  ProductID int identity(1,1) PRIMARY KEY, -- Clustered Unique Index created
  ProductName nvarchar(64) not null UNIQUE, -- Non-Clustered Unique Index created
  ModifiedDate date default(getdate()));
 
CREATE TABLE ProductPhoto (
  ProductPhotoID int identity(1,1) PRIMARY KEY, -- Clustered Unique Index created
  ProductID int REFERENCES Product(ProductID),
  LargePhoto varbinary(max),
  ModifiedDate date default(getdate()));

USE tempdb;

SELECT *

INTO   SODetail

FROM   AdventureWorks2008.Sales.SalesOrderDetail

GO

-- (121317 row(s) affected)

SELECT   TOP 100 *

FROM     SODetail

ORDER BY SalesOrderID,

         SalesOrderDetailID

;

WITH cteDistinctSO

     AS (SELECT DISTINCT SalesOrderID

         FROM   SODetail)

SELECT   [SequentialID] = Identity(INT,1,1),

         SalesOrderID

INTO     #SequentialMapping

FROM     cteDistinctSO

ORDER BY SalesOrderID ASC

GO

--(31465 row(s) affected) 

SELECT   TOP 10 *

FROM     #SequentialMapping

ORDER BY SalesOrderID

GO

-- SQL Server sequential update

UPDATE s

SET    s.SalesOrderID = m.[SequentialID]

FROM   SODetail s

       INNER JOIN #SequentialMapping m

         ON s.SalesOrderID = m.SalesOrderID 

GO

               

SELECT   TOP 100 *

FROM     SODetail

ORDER BY SalesOrderID,

         SalesOrderDetailID

DROP TABLE tempdb.dbo.SODetail

DROP TABLE #SequentialMapping

GO