sql server - sql updating column of table whose values come by group by on other table column -

i have 2 table subtopics , userinteractionlog . subtopics have timespent column want update timespent column , value come userinteractionlog using sum(datediff(mi,starttime,endtime)) group subtopicid

this have tried not working...

update subtopics s set timespent =  (    select sum(datediff(mi,u.starttime,u.endtime))   userinteractionlog u   group u.subtopicid having s.idsubtopic=u.subtopicid ) 

create table userinteractionlog ( id int , starttime datetime , endtime datetime , subtopicid int ) go  insert userinteractionlog(id,  starttime, endtime, subtopicid) values(1,   '2014-01-01 00:00:00.000',  '2014-03-02 00:00:00.000',  1) ,(2,    '2014-05-04 00:00:00.000',  '2014-06-06 12:00:00.000',  1) ,(3,    '2013-01-01 00:00:00.000',  '2013-01-02 00:00:00.000',  2)  create table subtopics ( timespent bigint , idsubtopic int ) go  insert subtopics (timespent, idsubtopic) values (null,  1) ,(null, 2) go  update subtopics set timespent =  (    select sum(datediff(mi,u.starttime,u.endtime))   userinteractionlog u   group u.subtopicid having idsubtopic=u.subtopicid ) go 

this returns

timespent   idsubtopic 134640       1 1440         2