Which database(s)? (please do speciify when you're asking DB/SQL questions.)
Do you have the database schema (table definitions)?
Do you expect us tio guess how your 会员发布产品信息表 is like?
会员id 信息 createdDate status(i.e. active or not)
Could you use views?
Could you update the a flag in table when you insert a 信息 for a 会员?
If you want plain SQL, I'm using MS SQL syntax now and assume the field names to be userid, message, createdDate, and status
-- specify N
select top N t1.userid, t1.message, t1.createdDate
from 产品信息表 t1
inner join (select userid, max(createdDate) latestDate from 产品信息表 where status='A' group by userid) t2
on t1.userid = t2.userid and t1.createdDate = t2.latestDate
order by t1.createdDate desc