mysql数据库 删除重复项 保留ts最新的项

sql语句是：

delete from table

where key in (select a. key key from (select * from table) a where niandu='2016' group  by a. key   having  count(a.key) > 1)

and ts not in (select max(b.ts) from  (select * fromtable)  b group by b.key having count(b.key )>1)

其中

 (select * from table) a 是为了在将table当成是子集，防止you cant specify  target table for update in from clause 错误。