请教一条sql
cid | uid | title |ctime...
12 | 134 | abc |2007-06-06
13 | 102 | def |2007-06-06
12 | 102 | def |2007-06-06
13 | 102 | def |2007-06-06
15 | 102 | def |2007-06-06
15 | 102 | def |2007-06-06
13 | 102 | def |2007-06-06
.. ... ..
要求
按时间顺序 每个公司id(cid)只取一条记录(所有字段)取top N条记录
请sql高手帮忙 谢谢 啦