Copy Nation procedure for Rooted World database

CopyNationRootedWorld.sql

CREATE PROCEDURE [dbo].[CopyNation]
    @id INT
AS
BEGIN
    SET NOCOUNT ON;
    SET XACT_ABORT ON;
    BEGIN TRAN;

    DECLARE @NationIDPairs TABLE (
        ExistingID INT NOT NULL UNIQUE,
        InsertedID INT NOT NULL UNIQUE
    );

    DECLARE @ProvinceIDPairs TABLE (
        ExistingID INT NOT NULL UNIQUE,
        InsertedID INT NOT NULL UNIQUE
    );

    MERGE INTO [dbo].[Nations] AS Target
    USING (
        SELECT *
        FROM [dbo].[Nations]
        WHERE [ID] = @id
    ) AS Source
    ON 1 = 0
    WHEN NOT MATCHED BY TARGET THEN
    INSERT (
        [Name],
        [FoundedDate])
    VALUES (
        Source.[Name],
        Source.[FoundedDate])
    OUTPUT Source.[ID], Inserted.[ID]
    INTO @NationIDPairs;

    MERGE INTO [dbo].[Provinces] AS Target
    USING (
        SELECT
            copy.*,
            j0.InsertedID j0InsertedID
        FROM [dbo].[Provinces] copy
        JOIN @NationIDPairs j0
            ON copy.[NationID] = j0.ExistingID
    ) AS Source
    ON 1 = 0
    WHEN NOT MATCHED BY TARGET THEN
    INSERT (
        [NationID],
        [Name],
        [Motto])
    VALUES (
        j0InsertedID,
        Source.[Name],
        Source.[Motto])
    OUTPUT Source.[ID], Inserted.[ID]
    INTO @ProvinceIDPairs;

    MERGE INTO [dbo].[Residents] AS Target
    USING (
        SELECT
            copy.*,
            j0.InsertedID j0InsertedID
        FROM [dbo].[Residents] copy
        JOIN @ProvinceIDPairs j0
            ON copy.[ProvinceID] = j0.ExistingID
    ) AS Source
    ON 1 = 0
    WHEN NOT MATCHED BY TARGET THEN
    INSERT (
        [ProvinceID],
        [Name])
    VALUES (
        j0InsertedID,
        Source.[Name]);

    COMMIT TRAN;
END;