从条件聚合结果中删除 NULLS

Question

我很难删除 NULLS。 ISNULL 语句似乎适用于动态结果，但不适用于第二个结果。

我的最终提取查询是：

select itemid,title,description,cat,fibre,washing,colours,promo,
   max(case when seqnum = 1 then isnull(chm_sizegrouping,'') end) as sizes_1,
   max(case when seqnum = 2 then isnull(chm_sizegrouping,'') end) as sizes_2,
   max(case when seqnum = 3 then chm_sizegrouping end) as sizes_3,
   max(case when seqnum = 4 then chm_sizegrouping end) as sizes_4)

显示的结果是：

itemid  sizes_1 sizes_2
LM008   one     NULL
LM009           NULL
LM010           NULL
lm011           NULL

非常感谢任何帮助，

谢谢。

Answer 1

不幸的是，您必须对每个可以检索 NULL 值的字段使用 ISNULL 函数。

Answer 2

试试这个：

select itemid,title,description,cat,fibre,washing,colours,promo,
       isnull(max(case when seqnum = 1 then chm_sizegrouping end),'') as sizes_1,
       isnull(max(case when seqnum = 2 then chm_sizegrouping end),'') as sizes_2,
........

Answer 3

只需将 ISNULL 检查放在 MAX() 函数的外部，如下所示：

select itemid,title,description,cat,fibre,washing,colours,promo,
    isnull(max(case when seqnum = 1 then chm_sizegrouping end), '') as sizes_1,
    isnull(max(case when seqnum = 2 then chm_sizegrouping end),'') as sizes_2,
    max(case when seqnum = 3 then chm_sizegrouping end) as sizes_3,
    max(case when seqnum = 4 then chm_sizegrouping end) as sizes_4)

从条件聚合结果中删除 NULLS

Removing NULLS from conditional aggregation results

sql

pivot

isnull