修正你的数据模型！您应该将所有数据放在一个表中，表中有一列 country . 然后你可以简单地做：

select country,
       count(custid) as custid_not_null,
       count(productid) as productid_not_null,
       count(addressid) as addressid_not_null
from all_countries
group by country ;

请注意 count(<expression>) 统计非- NULL 表达式的值。这个 case 表达完全是多余的。
如果没有，您可以创建一个视图：

create view all_counties as
    select 'malaysia' as country, t.*
    from malaysia m
    union all
    select 'thailand' as country, t.*
    from thailand t
    union all
    . . .;

但我建议你把所有的数据放在一张表里。

您需要稍微更改一下sql。用sum代替count。为了更好的分析，我增加了总数。我没有任何简单的方法，但你可以把列列表放在xl中，并从中创建一个公式，自动创建这个字符串 SUM(CASE WHEN custid IS NOT NULL then 1 ELSE 0 END) as "Nullcustid" .

select 
COUNT(*) "TotalCount",
SUM(CASE WHEN custid IS NOT NULL then 1 ELSE 0 END) as "NullCust",
SUM(CASE WHEN productid IS NOT NULL then 1 ELSE  0 END) as "Nullprod",
SUM(CASE WHEN addressid IS NOT NULL then 1 ELSE 0 END) as "Nulladdress" 
from malaysia 
union
select 
COUNT(*) "TotalCount",
SUM(CASE WHEN custid IS NOT NULL then 1 ELSE 0 END) as "NullCust",
SUM(CASE WHEN productid IS NOT NULL then 1 ELSE  0 END) as "Nullprod",
SUM(CASE WHEN addressid IS NOT NULL then 1 ELSE 0 END) as "Nulladdress" 
from thailand