create table A(BH varchar(20),SL decimal(18,1))
insert into A values('6W801' ,        10 )
insert into A values('5W6801',        20 )
insert into A values('2W7011',        15 )
insert into A values('3W652' ,        11 )
create table B(BH varchar(20),SL decimal(18,1))
insert into B values('6W801-A-JB',    6  )
insert into B values('5W6801-SH' ,    5.5) 
insert into B values('2W7011-X'  ,    8  )
insert into B values('3W652-C'   ,    9  )
go
select a.bh , a.sl asl,b.sl as bsl from a,b
where (a.bh = b.bh) or (a.bh = left(b.bh,charindex('-',b.bh)-1) and charindex('-',b.bh) > 0)
drop table A,B

/*
bh                   asl                  bsl                  
-------------------- -------------------- -------------------- 
6W801                10.0                 6.0
5W6801               20.0                 5.5
2W7011               15.0                 8.0
3W652                11.0                 9.0

（所影响的行数为 4 行）
*/

------解决方案--------------------
create table t1                    
(BH  varchar(10)      ,     SL   int      )
insert into t1
select '6W801' ,        10 union all  
select '5W6801',        20 union all  
select '2W7011',        15 union all
select '3W652' ,        11  



create table t2                 
(BH  varchar(100),            ZL         numeric(10,2))
insert into t2

select '6W801-A-JB',     6  union all
select '5W6801-SH' ,    5.5 union all  
select '2W7011-X'  ,    8   union all
select '3W652-C'   ,    9  



select a.* ,b.* from
t1 a join t2 b
on a.BH=LEFT(b.BH,charindex('-',b.BH)-1)


BH         SL          BH                                                                                                   ZL          
---------- ----------- ---------------------------------------------------------------- ------------  
6W801      10          6W801-A-JB                                                                                           6.00
5W6801     20          5W6801-SH                                                                                            5.50
2W7011     15          2W7011-X                                                                                             8.00
3W652      11          3W652-C                                                                                              9.00

（所影响的行数为 4 行）

------解决方案--------------------
 SELECT TAB1.BH,TAB1.SL,TAB2.ZL FROM TAB1 JOIN TAB2 ON CHARINDEX(TAB1.BH,TAB2.BH)>0  
WHERE LTRIM(TAB2.BH,LEN(TAB1.BH)) IN ('-A','-JB','-SH','-C','-A-JB')
----
没测试过，让您见笑了