case when 表达式 is null then 0 end ，结果一直是null

[iiiiiiiii_z]

case when 表达式 is null then 0 end
我这里的表达式是一个select 语句，我的想法是表达式如果查出来不为null就是自身的值（如，10,23,78...）,为null是0，但是现在有值一直是null。

select d.fjmc1 as 辅具名称,d.fjbh1 as 产品编号,
		sum(case when  d.fjsx1='成品'  and  d.chaptertype='1' then 1 else 0 end ) as A目录,
		sum(case when  d.fjsx1='成品' and d.chaptertype='2'  then 1 else 0 end ) as B目录,
		sum(case when  d.fjsx1='成品' then 1 else 0 end ) as 合计,
		sum(case when  d.fjsx1='定制品' or d.fjsx1='改制品'  then 1 else 0 end ) as "定改制(件)",
(
case when (SELECT 	sum(convert(int,cast(b.dj1 as float))	*convert(int,cast(b.sl1 as float))	) 
		from  dsass_zwb_fjkffwxq a INNER JOIN dsassfjfjpsdjb b on a.ida_psdj=b.id where b.fjbh1 is not null  and  b.chaptertype='1') is null then 0  end
)  as A目录a,
( 
case when (SELECT 	sum(convert(int,cast(b.dj1 as float))	*convert(int,cast(b.sl1 as float))	) 
		from  dsass_zwb_fjkffwxq a INNER JOIN dsassfjfjpsdjb b on a.ida_psdj=b.id where b.fjbh1 is not null  and  b.chaptertype='2') is null then 0 end

) as B目录a ,
((SELECT 		sum(convert(int,cast(b.dj1 as float))	*convert(int,cast(b.sl1 as float))	)
		from  dsass_zwb_fjkffwxq a INNER JOIN dsassfjfjpsdjb b on a.ida_psdj=b.id where b.fjbh1 is not null  and  b.chaptertype='1')+
(SELECT 	sum(convert(int,cast(b.dj1 as float))	*convert(int,cast(b.sl1 as float))	) 
		from  dsass_zwb_fjkffwxq a INNER JOIN dsassfjfjpsdjb b on a.ida_psdj=b.id where b.fjbh1 is not null  and  b.chaptertype='2')) as 合计
	
from  dsass_zwb_fjkffwxq c INNER JOIN dsassfjfjpsdjb d on c.ida_psdj=d.id where d.fjbh1 is not null GROUP BY d.fjmc1,d.fjbh1

[卖水果的net]

case when 表达式 is null then 0 end 换成 isnull(表达式, 0)

[zbdzjx]

case when 表达式 is null then 0 end 要改成 case when 表达式 is null then 0 else 表达式 end 或者用楼上的：isnull(表达式, 0)