SQL选择行如果其他表中不存在任何行

您可以

not exists

select * fromdb_users dbuwhere not exists (    select 1 from db_likes dbl    where dbl.relation in ('dislike','like','maybe') -- not sure if this is necessary    and dbl.user = $oUser->id    and dbl.partner = dbu.id)

http://sqlfiddle.com/#!2/8c3bb9/6