mysql中not in子查询不能为空

转载自：https://blog.csdn.net/headingalong/article/details/77744755

错误sql

delete
from
  company_info
where id NOT in
  (SELECT
      company_info_ID
    FROM
      USER);

因为null的原因，导致出现子查询的结果为空。

正确的写法是

-- 清除重复的不可用的公司信息
delete
from
  company_info
where id NOT in
  (SELECT
      company_info_ID
    FROM
      USER
      where company_info_ID is not null);