下列情形不属于不当得利的是（ )。

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SQL Error: select id,body,options from ***_enewstiku where sourceid='31904' and id < 2550692 and id<>'2550692' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku where sourceid='31904' and id > 2550692 and id<>'2550692' order by id asc limit 5