想要到达的效果是null值 则sql 拼接t.province_code is null 如下图alert出来的值 但是怎么都传不过 打印出来的sql是 and t.province_code in('null') 请问该怎么拼接 ${if(len(province_code)==0||province_code=="''"||province_code== null||isnull(province_code)," t.province_code is null "," and t.province_code in('" + province_code + "')")}