Integer 指导主键数据库迁移

Question

我正在尝试从基于 int 的主键迁移到基于 guid 的系统，但在迁移自引用表时遇到了问题

Entity
---------
ID
ParentID
AnotherParentID

查询表时，我正在为每一行创建新的 guid ID ，但是如何为具有该ID作为ParentID或AnotherParentID字段上的外键的行设置相同的 guid 值？

SELECT 
    newid() as ID,
    (SELECT e.ID ...?) as ParentID,
    (SELECT e.ID ...?) as AnotherParentID,
FROM Entity e

Answer 1

如果 paretnID 是外键：

Select NEWID(), ID, EP.ParentIDGUID, E.ParentID, EP2.AnotherParentID, EP2.AnotherParentIDGUID from dbo.Entity E  
        INNER JOIN 
        (Select MAX(NEWID()) as ParentIDGUID, ParentID FROM dbo.Entity GROUP BY ParentID) EP ON EP.ParentID = E.ParentID
        INNER JOIN 
        (Select MAX(NEWID()) as AnotherParentIDGUID, AnotherParentID FROM dbo.Entity GROUP BY AnotherParentID) EP2 ON EP2.AnotherParentID = E.AnotherParentID

或者如果它们是同一张表上的外键：

Select NEWID() as guidID, ID
INTO #tp 
 from dbo.Entity E


Select EP.ID, EP.guidID, E.ParentID, EP2.guidID, E.AnotherParentID, EP3.guidID from dbo.Entity E  
    INNER JOIN 
    #tp EP ON EP.ID = E.ID
    INNER JOIN 
    #tp EP2 ON EP2.ID = E.ParentID
    INNER JOIN 
    #tp EP3 ON EP3.ID = E.AnotherParentID


DROP TABLE #tp 

Answer 2

@MRsa 答案给出了多行，因为加入了ParentID或AnotherParentID （因为多行可以具有相同的 ParentID/AnotherParentID）。

这是我当前有效的实现，我不确定是否有更好的方法来处理这个

CREATE TABLE #tmp (
    Id uniqueidentifier null,
    OldId integer null
)

INSERT INTO #tmp (Id, OldId)
SELECT NEWID(), Id FROM OldTable

INSERT INTO NewTable
SELECT
    (SELECT Id FROM #tmp WHERE OldId = i.Id) as ID,
    (SELECT Id FROM #tmp WHERE OldId = i.ParentId) as ParentID,
    (SELECT Id FROM #tmp WHERE OldId = i.AnotherParentID) as AnotherParentID,
FROM OldTable i