MySQL 错误 : NOT IN + subquery using GROUP BY HAVING returns nothing

Question

我正在查询这张表:

SKU
aaaa
bbbb
bbbb
NULL

这是查询:

select *
from TEST as N                                      
where  N.SKU NOT IN (select SKU
                     from TEST
                     group by SKU
                     having count(*)>1);

我希望查询返回“aaaa”，但是它什么也没返回。

我期望的原因是因为下面的子查询只返回'bbbb':

select SKU
from TEST
group by SKU
having count(*)>1   

因此，'aaaa' 不在子查询结果中。

要显示错误，请将这些语句复制并粘贴到您的 MySQL IDE 中以创建模式:

drop table if exists TEST;
create table TEST(
SKU varchar(255)
);
insert into TEST values('aaaa'),('bbbb'),('bbbb'),(NULL);

Answer 1

这工作正常，如果子查询只返回一行:

SELECT * 
FROM TEST as N 
WHERE N.SKU NOT IN (
  CAST((select SKU from TEST group by SKU having count(*)>1) AS CHAR)
)

但是，如果它返回多于 1 行，则会触发错误。另一种解决方案(如果子查询返回多于 1 行):

SELECT * 
FROM TEST as N 
WHERE N.SKU IN (
  (select SKU from TEST group by SKU having count(*) <= 1)
)