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你打算從SQL Server 2000數(shù)據(jù)庫的客戶表和國別表中導(dǎo)入客戶數(shù)據(jù)到SQL Server 2005數(shù)據(jù)庫中。你要確保在導(dǎo)入過程中，客戶表中國家代碼列的每個(gè)值在SQL Server 2005數(shù)據(jù)庫中國別表內(nèi)都有其相應(yīng)的紀(jì)錄。你在兩個(gè)表之間定義一外鍵，這樣，參照完整性將保證若國家代碼值在客戶表中存在，而在國別表中不存在時(shí)導(dǎo)入程序失敗。你要確保國別表無記錄時(shí)導(dǎo)入過程不失敗，該怎么做？（）

You are planning to import customer data from the Customer table and the Country table in your SQL Server 2000 database into a SQL Server 2005 database. You want to ensure that during the import process，each value in the CountryCode column of the Customer table has a corresponding record in the CountryCode column in the Country table of the SQL Server 2005 database. You define a foreign key between these two tables. Thus，referential integrity will guarantee that the import routine fails if there are any records where a CountryCode value does not exist in the Country table but does exist in the Customer table. You need to ensure that the import process does not fail if records are encountered that do not exist in the Country table.
What should you do？（）