select *
from (select *,row_number()over(partition by sfzh order by xm) as row from table1)t
where row=1

------解决方案--------------------
SQL code
select tid=identity(int,1,1),* into # from A

select xm,sfzh,ab,bc from # t
  where not exists(select 1 from # where sfzh=t.sfzh and tid<t.tid)

drop table #

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

表中要有唯一ID
delete from 表
where 字段1 in (select 字段1 from 表 group by 字段1 having count(字段1)>1) and
 ID not in(select min(id) from 表 group by 字段1 having count(字段1)>1)