im going to fetch records from 4 table in one query just getting error in "not equal" oprater "<>" i dont why its not working i also try to use "!=" but same result. please check and let me know if there is something worng or how to im able to fix problem.

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select en.*, nt.*, mt.*, nl.*, en.id as en_id, en.title as en_title, mt.id as mt_id from {tbl}expiration_notice en, {tbl}noticetype nt, {tbl}mailtemp mt, {tbl}noticelogs nl where en.type=nt.id and nt.id=mt.parentid and en.expirytime<($shonirvartime+(".(60*60*24)."*mt.d ays)) and nl.noticeid<>en.id and nl.mailid<>mt.id
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thanks in advance for your consideration