如何将迁移数据复制到具有标识列的新表，同时保留 FK 关系？

Question

我想将数据从一个数据库迁移到另一个数据库。表模式完全相同：

CREATE TABLE Customers(
    [Id] INT NOT NULL PRIMARY KEY IDENTITY,
    (some other columns ......)
);

CREATE TABLE Orders(
    [Id] INT NOT NULL PRIMARY KEY IDENTITY,
    [CustomerId] INT NOT NULL,
    (some other columns ......),
    CONSTRAINT [FK_Customers_Orders] FOREIGN KEY ([CustomerId]) REFERENCES [Customers]([Id])
)

两个数据库有不同的数据，因此同一个表的新身份密钥在两个数据库中会不同。这不是问题；我的目标是将新数据附加到现有数据中，而不是完全替换整个表的所有数据。但是我想维护插入数据的所有父子关系。

如果我使用 SSMS 的“生成脚本”功能，脚本将尝试使用相同的 ID 插入，这会与目标数据库中的现有数据发生冲突。如何仅使用数据库脚本复制数据？

我希望目的地的标识列从其最后一个值正常继续。

Customers没有任何其他UNIQUE NOT NULL约束。它是确定在其他列重复数据（我使用的是Customers与Orders只是作为一个例子在这里，所以我没有解释整个故事）。问题是关于任何一对 N 关系。

Answer 1

这是一种可以轻松扩展到三个相关表的方法。

使用 MERGE 将数据插入到副本表中，以便您可以将旧的和新的 IDENTITY 值输出到控制表中，并将它们用于相关表的映射。

实际答案只是两个 create table 语句和三个合并。其余的是样本数据设置和拆卸。

USE tempdb;

--## Create test tables ##--

CREATE TABLE Customers(
    [Id] INT NOT NULL PRIMARY KEY IdENTITY,
    [Name] NVARCHAR(200) NOT NULL
);

CREATE TABLE Orders(
    [Id] INT NOT NULL PRIMARY KEY IdENTITY,
    [CustomerId] INT NOT NULL,
    [OrderDate] DATE NOT NULL,
    CONSTRAINT [FK_Customers_Orders] FOREIGN KEY ([CustomerId]) REFERENCES [Customers]([Id])
);

CREATE TABLE OrderItems(
    [Id] INT NOT NULL PRIMARY KEY IdENTITY,
    [OrderId] INT NOT NULL,
    [ItemId] INT NOT NULL,
    CONSTRAINT [FK_Orders_OrderItems] FOREIGN KEY ([OrderId]) REFERENCES [Orders]([Id])
);

CREATE TABLE Customers2(
    [Id] INT NOT NULL PRIMARY KEY IdENTITY,
    [Name] NVARCHAR(200) NOT NULL
);

CREATE TABLE Orders2(
    [Id] INT NOT NULL PRIMARY KEY IdENTITY,
    [CustomerId] INT NOT NULL,
    [OrderDate] DATE NOT NULL,
    CONSTRAINT [FK_Customers2_Orders2] FOREIGN KEY ([CustomerId]) REFERENCES [Customers2]([Id])
);

CREATE TABLE OrderItems2(
    [Id] INT NOT NULL PRIMARY KEY IdENTITY,
    [OrderId] INT NOT NULL,
    [ItemId] INT NOT NULL,
    CONSTRAINT [FK_Orders2_OrderItems2] FOREIGN KEY ([OrderId]) REFERENCES [Orders2]([Id])
);

--== Populate some dummy data ==--

INSERT Customers(Name)
VALUES('Aaberg'),('Aalst'),('Aara'),('Aaren'),('Aarika'),('Aaron'),('Aaronson'),('Ab'),('Aba'),('Abad');

INSERT Orders(CustomerId, OrderDate)
SELECT Id, Id+GETDATE()
FROM Customers;

INSERT OrderItems(OrderId, ItemId)
SELECT Id, Id*1000
FROM Orders;

INSERT Customers2(Name)
VALUES('Zysk'),('Zwiebel'),('Zwick'),('Zweig'),('Zwart'),('Zuzana'),('Zusman'),('Zurn'),('Zurkow'),('ZurheIde');

INSERT Orders2(CustomerId, OrderDate)
SELECT Id, Id+GETDATE()+20
FROM Customers2;

INSERT OrderItems2(OrderId, ItemId)
SELECT Id, Id*1000+10000
FROM Orders2;

SELECT * FROM Customers JOIN Orders ON Orders.CustomerId = Customers.Id JOIN OrderItems ON OrderItems.OrderId = Orders.Id;

SELECT * FROM Customers2 JOIN Orders2 ON Orders2.CustomerId = Customers2.Id JOIN OrderItems2 ON OrderItems2.OrderId = Orders2.Id;

--== ** START ACTUAL ANSWER ** ==--

--== Create Linkage tables ==--

CREATE TABLE CustomerLinkage(old INT NOT NULL PRIMARY KEY, new INT NOT NULL);
CREATE TABLE OrderLinkage(old INT NOT NULL PRIMARY KEY, new INT NOT NULL);

--== Copy Header (Customers) rows and record the new key ==--

MERGE Customers2
USING Customers
ON 1=0 -- we just want an insert, so this forces every row as unmatched
WHEN NOT MATCHED THEN
INSERT (Name) VALUES(Customers.Name)
OUTPUT Customers.Id, INSERTED.Id INTO CustomerLinkage;

--== Copy Detail (Orders) rows using the new key from CustomerLinkage and record the new Order key ==--

MERGE Orders2
USING (SELECT Orders.Id, CustomerLinkage.new, Orders.OrderDate
FROM Orders 
JOIN CustomerLinkage
ON CustomerLinkage.old = Orders.CustomerId) AS Orders
ON 1=0 -- we just want an insert, so this forces every row as unmatched
WHEN NOT MATCHED THEN
INSERT (CustomerId, OrderDate) VALUES(Orders.new, Orders.OrderDate)
OUTPUT Orders.Id, INSERTED.Id INTO OrderLinkage;

--== Copy Detail (OrderItems) rows using the new key from OrderLinkage ==--

MERGE OrderItems2
USING (SELECT OrderItems.Id, OrderLinkage.new, OrderItems.ItemId
FROM OrderItems 
JOIN OrderLinkage
ON OrderLinkage.old = OrderItems.OrderId) AS OrderItems
ON 1=0 -- we just want an insert, so this forces every row as unmatched
WHEN NOT MATCHED THEN
INSERT (OrderId, ItemId) VALUES(OrderItems.new, OrderItems.ItemId);

--== ** END ACTUAL ANSWER ** ==--

--== Display the results ==--

SELECT * FROM Customers2 JOIN Orders2 ON Orders2.CustomerId = Customers2.Id JOIN OrderItems2 ON OrderItems2.OrderId = Orders2.Id;

--== Drop test tables ==--

DROP TABLE OrderItems;
DROP TABLE OrderItems2;
DROP TABLE Orders;
DROP TABLE Orders2;
DROP TABLE Customers;
DROP TABLE Customers2;
DROP TABLE CustomerLinkage;
DROP TABLE OrderLinkage;