select dtype INTO #tmptble from table2 where uid in (select uid from table2)

update table1 set dtype=(select top 1 dtype from #tmptble where table1.uid=#tmptble.uid)

------解决方案--------------------
楼上有误。

SQL code


select dtype INTO #tmptble from table2 where uid in (select uid from [color=#FF0000]table1[/color])

update table1 set dtype=(select top 1 dtype from #tmptble where table1.uid=#tmptble.uid)

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

create table tab1_uid as 
select distinct uid from table1;

create index idx1 on  tab1_uid(uid);

create table tab2_uid as 
select a.uid , a.dtype
from table2 a inner join tab1_uid b on a.uid = b.uid

update table1 a, tab2_uid b 
set a.dtype = b.dtype
where a.uid = b.uid