在控制条件下人为地改变某些变量（自变量）来观测其他变量的变化的方法是

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SQL Error: select id,body,options from ***_enewstiku where sourceid='24419' and id < 2103012 and id<>'2103012' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku where sourceid='24419' and id > 2103012 and id<>'2103012' order by id asc limit 5