insert into b(id)
select uaserid from A
union all
select uaserid1 from A
union all
select uaserid2 from A
union all
select uaserid3 from A

------解决方案--------------------
SQL code
if object_id('A') is not null drop table A go
select 1 as uaserid,3 as uaserid1,4 as uaserid2,5 as uaserid3 into A

if object_id('B') is not null drop table B go
select a.uaserid1 as ID 
into B
from (select uaserid1 from A union all
      select uaserid2 from A union all
      select uaserid3 from A) a

select * from B

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

insert into b(id)
select uaserid1 from A
union all
select uaserid2 from A
union all
select uaserid3 from A

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

create function [dbo].[m_split](@c varchar(2000),@split varchar(2))   
  returns @t table(col varchar(200))   
  as   
    begin   
      while(charindex(@split,@c)<>0)   
        begin   
          insert @t(col) values (substring(@c,1,charindex(@split,@c)-1))   
            set @c = stuff(@c,1,charindex(@split,@c),'')   
        end   
      insert @t(col) values (@c)   
      return   
end

go
--定义@表A,@表B
declare @表A table (uaserid int,uaserid1 nvarchar(20),uaserid2 nvarchar(20),uaserid3 nvarchar(20))
insert into @表A
select 1,3,4,5

declare @表B table (id int)

declare @t varchar(20)
select @t= uaserid1+','+uaserid2+','+uaserid3 from @表A
--插入数据
insert into @表B
select * from dbo.m_split(@t,',')
--查询结果
select * from @表B
/*
id
-----------
3
4
5
*/