这条sql语句怎么写？

Question

A表的字段以及记录如下：
usercode   time      expendtime    projcode
zhangsan  2012-5-10       5               proj1
lisi  2012-4-12       8               proj2
wangwu  2012-5-10       5          proj3
zhaoliu  2012-4-20       3               proj4
zhangsan  2012-5-10       5               proj2
zhaoliu  2012-5-15       6               proj6
我想得到下面的结果
usercode     projs        sum(expendtime)
zhangsan  proj1、proj2   10
lisi  proj2             8
wangwu  proj3             5
zhaoliu  proj4、proj6    8
该怎么写sql，关键是中间那一列？

Answer 1

select usercode,wm_concat(projcode),sum(expendtime)
  from t
 group by usercode;