这条sql语句怎么写？
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？



------解决方案--------------------

SQL code

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