一个sql语句

declare @ta table(a int,  b int)
insert into @ta values(1,  3)
insert into @ta values(2,  4)
insert into @ta values(1,  43)

declare @tb table(a int,  c int)
insert into @tb values(1,  3)
insert into @tb values(3, 4)

update @tb
set c = a.b
from @tb b, (select a, sum(b) as b from @ta group by a) a
where b.a = a.a

select * from @tb