SQL Server 업데이트 트리거에서 수정된 필드만 효율적으로 검색하는 방법은 무엇입니까?

CREATE TRIGGER TriggerName ON dbo.Sample_Table FOR DELETE, INSERT, UPDATE AS
BEGIN
    SET NOCOUNT ON;

    -- Unpivot deleted
    WITH deleted_unpvt AS (
        SELECT ContactID, FieldName, FieldValue
        FROM (SELECT ContactID, Forename, Surname, Extn, Email, Age FROM deleted) p
        UNPIVOT (FieldValue FOR FieldName IN (Forename, Surname, Extn, Email, Age)) AS deleted_unpvt
    ),
    -- Unpivot inserted
    inserted_unpvt AS (
        SELECT ContactID, FieldName, FieldValue
        FROM (SELECT ContactID, Forename, Surname, Extn, Email, Age FROM inserted) p
        UNPIVOT (FieldValue FOR FieldName IN (Forename, Surname, Extn, Email, Age)) AS inserted_unpvt
    )

    -- Join them and identify changes
    INSERT INTO Sample_Table_Changes (ContactID, FieldName, FieldValueWas, FieldValueIs)
    SELECT Coalesce(D.ContactID, I.ContactID) ContactID,
           Coalesce(D.FieldName, I.FieldName) FieldName,
           D.FieldValue AS FieldValueWas,
           I.FieldValue AS FieldValueIs
    FROM deleted_unpvt D
    FULL OUTER JOIN inserted_unpvt I
        ON D.ContactID = I.ContactID AND D.FieldName = I.FieldName
    WHERE D.FieldValue <> I.FieldValue
    OR (D.FieldValue IS NOT NULL AND I.FieldValue IS NULL)
    OR (D.FieldValue IS NULL AND I.FieldValue IS NOT NULL);
    
    -- Use the contents of Sample_Table_Changes for replication
END
GO