Oracle decode()处理被除数为0

　　decode (expression, search_1, result_1)　　如果 expression结果＝search_1结果，则返回result_1　　decode (expression, search_1, result_1, search_2, result_2)　　decode (expression, search_1, result_1, search_2, result_2, ...., search_n, result