insert into B
 select row_number() over(order by getdate()),*
 from (select Uname,Uage from A union all select NAME,AGE from A) t

------解决方案--------------------
SQL code
B表中Uid 是自增列么？如果是的可以

insert into b(uname,uage) select name,age from a

------解决方案--------------------
insert into  b select column1,column2,column2 from a;---向现有数据结构表中添加数据
select * into new_tablename from old_tablename---复制一个现有表结构并将其数据追加到新表结构中

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

insert into b(uname,uage) select name,age from a