请教sql求和

数据库里有value字段，他的值有正数也有负数，我想用sql语句求出正数与正数的合，负数与负数的和 用case语句怎么写

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SQL code:
select 正数和=sum(case when value>0 then value else 0 end),
负数和=sum(case when value<0 then value else 0 end)
from tb

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SQL code:
select sum(case when value>0 then Valu end),
sum(case when value<0 then Valu end)
from tb

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SQL code:
select
case when a>=0 then '正数和0' else '负数' end,
sum(value)
from tb
group by
case when a>=0 then '正数和0' else '负数' end

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接分，学习。

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SQL code:
select
case when [value]>=0 then '正数和0' else '负数' end,
sum([value])
from tb
group by
case when [value]>=0 then '正数和0' else '负数' end

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SQL code:

select sum(case when value>=0 then value else 0 end),
sum(case when value<0 then value else 0 end)
from tb

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select sum(