update tbl1 set type=a.type from tbl2 a where a.uid=tbl1.uid

------解决方案--------------------
SQL code

create table #t1(id int, xtype char(1))
insert into #t1 select 1,NULL
union all select 2,NULL
union all select 2,NULL
union all select 3,NULL
union all select 4,NULL


create table #t2(id int, xtype char(1))
insert into #t2 select 1,'a'
union all select 2,'b'
union all select 3,'c'
union all select 4,'d'

update #t1 set xtype=(select xtype from #t2 where #t1.id=#t2.id)

select * from #t1

-----------------------------------

id          xtype
----------- -----
1           a
2           b
2           b
3           c
4           d

(5 行受影响)