这是密码。我检查了好几次，但一切都正常。我可能还没找到等号，或者是别的原因？

MERGE INTO existing_customers c
USING new_customers n
ON (c.customer_id = n.customer_id)
WHEN MATCHED THEN
    UPDATE SET
    c.first_name = n.first_name,
    c.last_name = n.last_name,
    c.address_state = n.address_state,
    c.email_address = n.email_address,
WHEN NOT MATCHED THEN
    INSERT (c.customer_id,c.first_name,c.last_name,c.address_state,c.email_address)
    VALUES (n.customer_id,n.first_name,n.last_name,n.address_state,n.email_address)