mysql - 如何获取不在下一个表mysql中的数据

Question

我有返回所有数据的 mysql 查询

SELECT state,`County`,`CountyFIPS`,count(`email_address`) as email 
FROM `campaign_emails` 
Where state='AK' 
  AND CountyFIPS NOT IN 
   (select group_concat(`county_fipscode` separator ',') 
    from order_cart where flyer_id='1' AND user_id='400'
   ) 
GROUP BY `CountyFIPS`

但是当我手动传递相同的查询时，它会返回我的确切值

SELECT state,`County`,`CountyFIPS`,count(`email_address`) as email 
FROM `campaign_emails` 
Where state='AK' 
  AND CountyFIPS NOT IN (02261,02220,02180,02170,02240,02020,02090,02110) 
GROUP BY `CountyFIPS`

请大家帮帮忙，请问是什么原因？

Answer 1

IN 接受 SELECT 查询的结果，但以逗号分隔值作为硬编码字符串的字符串仅被视为 1 个值，因此所有内容都将在您的第一个查询中匹配。

Mysql 在第一个查询中看到您的条件为:

... AND CountyFIPS NOT IN ('1,2,3,4,5')    // this is not the array of values you want to use

因此您可以将代码简化为:

SELECT state,County,CountyFIPS,count(email_address) as email
FROM campaign_emails Where state='AK' 
    AND CountyFIPS NOT IN (select county_fipscode from order_cart where flyer_id='1' AND user_id='400') GROUP BY CountyFIPS
                                  ^^^^^^^^^^^^^^^ here