先记录一段代码，之后做医院成本分摊项目用

# todo 获取客户产品编码:
    def _get_partner_product(self, partner, product_id):
        sql = """SELECT cp.partner_default_code FROM customer_product cp
                LEFT JOIN res_partner rp ON rp.id = cp.partner_id
                WHERE cp.product_id = %s AND cp.partner_id = %s"""
        self.cr.execute(sql, (product_id, partner))
        sql_data = self.cr.fetchall()
        if len(sql_data) > 0:
            for obj in sql_data:
                partner_default_code = obj[0]
            return partner_default_code
        return ''

此代码关键在于 left join用于表之间合并关联查询