select 
  a.number, bc.user, d.username
from
  a left join
  (select name, user from b union all
   select name, user from c) bc on a.name = bc.name left join
  d on a.id = d.id

------解决方案--------------------
 select a.number,bc.user,d.username
  from a,d,(select name,user from b union select name,user from c)bc
  where a.name=bc.name
  and   a.id=d.id


------解决方案--------------------
union关联了。

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

with ta as(
     select '1001' id,'第一号机器' name,10 num from dual union all
     select '1002','第二号机器',20 from dual union all
     select '1003','第三号机器',30 from dual union all
     select '1004','第四号机器',40 from dual union all
     select '1005','第五号机器',50 from dual)
,tb as(
    select '第一号机器' name,'Operator' users from dual union all
    select '第四号机器','Manager' from dual union all
    select '第三号机器','Manipulator' from dual)
,td as(
    select '1001' id,'James' user_name from dual union all
    select '1002','Smith' from dual union all
    select '1003','Scott' from dual union all
    select '1004','Jim' from dual)
select ta.id,ta.name,tb.users,td.user_name
from ta,tb,td
where ta.id=td.id --使用等值连接即可
  and ta.name=tb.name
/
ID   NAME       USERS       USER_NAME
---- ---------- ----------- ---------
1001 第一号机器 Operator    James
1003 第三号机器 Manipulator Scott
1004 第四号机器 Manager     Jim