case when xs>sg or spid in(个别spid) then xs 

else sg end 

优先判断一下你特殊的编码，再判断是否大于，

case when spid in('A1005','B1345','A444') then xs 

when xs>sg then xs else sg end end as 判断后

select rq,spid,xs,sg,

case when  spid='xxx' then xs

 when  xs>sg then xs else sg end 

from a

where rq>=

and rq<=

select 

rq,

spid,

xs,

sg,

case when spid in(spid01,spid02,spid03) or xs>sg then xs 

else sg end type

    from a

    where rq>=

        and rq<=

type：结果字段别名

spid01,spid02,spid03：所谓的个别spid