磁盘的盘面上有很多半径不同的同心圆，这些同心圆称为 。

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SQL Error: select id,body,options from ***_enewstiku where sourceid='29992' and id < 2430580 and id<>'2430580' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku where sourceid='29992' and id > 2430580 and id<>'2430580' order by id asc limit 5