--如果位置固定
select substring(name,5,3) from tb
--如果位置不固定
select substring(name , charindex('-',name)+1 , charindex('-',name,charindex('-',name)+1) - charindex('-',name) -1) from tb

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

位置不固定
declare @str1 nvarchar(100),@str2 nvarchar(100)
set @str1 = 'ddddddqq_bbdddqq_cccc_eee' 
set @str2=stuff(@str1,charindex('_',@str1,1),1,'m')
select substring(@str1,charindex('_',@str1,1)+1,charindex('_',@str2,1)-charindex('_',@str1,1)-1)

------解决方案--------------------
create table b (name varchar(50))
insert b select 'dfsdfds_dddfa_fsdfa_dsfasd'  union all select  
'sdfsdaf_fdsfg_fds_fsdafs' union all select  
'dafasdf_fasdf_fdsfsd' union all select  
'sdfds_dsfasd'  
select substring(name , charindex( '_',name+'_')+1 , charindex( '_',name+'_',charindex( '_',name+'_')+1) - charindex( '_',name+'_') -1) from b  


------解决方案--------------------
SQL code
create function kkk(@text varchar(100))
returns varchar(50)
as
begin
    declare @p varchar(50)
    declare @num int
    if(charindex('_',@text)>0)
    begin
        set @text=substring(@text,charindex('_',@text)+1,len(@text))
        set @num=charindex('_',@text)
        if(@num>0)set @p=substring(@text,1,charindex('_',@text)-1)
        else set @p=@text
    end
    return @p
end

调用
select dbo.kkk('_bbb_asdf')

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

declare @num int
declare @str1 nvarchar(100),@str2 nvarchar(100)
set @str1 = '_bbdddqqeee_' 
set @str2=stuff(@str1,charindex('_',@str1,1),1,'m')
if(charindex('_',@str2,1)>charindex('_',@str1,1))
   set @num=charindex('_',@str2,1)-charindex('_',@str1,1)-1
else
   set @num=len(@str1)-charindex('_',@str1,1)
select substring(@str1,charindex('_',@str1,1)+1,@num)
/*
----------------------------------------
bbdddqqeee

*/

------解决方案--------------------
可以在字符的后面先加上个'_',这样应该就可以了


declare @name as varchar(20)
set @name = 'qqq_bbb_cccc_eee' + '_'

select 位置固定 = substring(@name , 5 ,3)  

select 位置不固定 = substring(@name , charindex('_',@name)+1 , charindex('_',@name,charindex('_',@name)+1) - charindex('_',@name) -1)