下列哪些现象中存在正反馈（      ）

试卷相关题目

SQL Error: select id,body,options from ***_enewstiku where sourceid='25931' and id < 2179238 and id<>'2179238' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku where sourceid='25931' and id > 2179238 and id<>'2179238' order by id asc limit 5