SELECT A.MA003 AS MB005, B.MA003 AS MB006, C.MA003 AS MB007, D.MA003 AS MB008, PN
FROM  表A LEFT OUTER JOIN 表B AS A ON 表A.MB005 = A.MA003
LEFT OUTER JOIN 表B AS B ON 表A.MB005 = B.MA003
LEFT OUTER JOIN 表B AS C ON 表A.MB005 = C.MA003
LEFT OUTER JOIN 表B AS D ON 表A.MB005 = D.MA003

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

create table #表A(MB005 varchar(4),MB006 varchar(4),MB007 varchar(4),MB008 varchar(4),PN varchar(4))
insert into #表A
select '113', 'null', 'null' ,'406','AA' union all
select '113', '311' , 'null' ,'406','BB' union all
select '112', 'null', '2190' ,'406','CC' 
 
create table #表B(MB002 varchar(4),MB003 varchar(10))
insert into #表B
select '113','实验品' union all
select '112','原材料' union all
select '311', '前处理' union all
select '2190','ROHS类' union all
select '406','大宗物品'

select B.MB003 MB003,C.MB003 MB006,D.MB003 MB007,E.MB003 MB008,A.PN PN from #表A A 
left join #表B B on A.MB005=B.MB002
left join #表B C on A.MB006=C.MB002
left join #表B D on A.MB007=D.MB002
left join #表B E on A.MB008=E.MB002

--结果
实验品    NULL    NULL    大宗物品    AA
实验品    前处理    NULL    大宗物品    BB
原材料    NULL    ROHS类    大宗物品    CC
--消息
(3 行受影响)

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

--道兄正解
SELECT a.ma003 AS mb005,
       b.ma003 AS mb006,
       c.ma003 AS mb007,
       d.ma003 AS mb008,
       pn
FROM   表a
       LEFT OUTER JOIN 表b AS a
         ON 表a.mb005 = a.ma003
       LEFT OUTER JOIN 表b AS b
         ON 表a.mb005 = b.ma003
       LEFT OUTER JOIN 表b AS c
         ON 表a.mb005 = c.ma003
       LEFT OUTER JOIN 表b AS d
         ON 表a.mb005 = d.ma003