Question

我的[Table1]具有用户ID，[Table2]具有相同的用户ID（左连接）和列“打开”，具有已读消息的数量。我想从[Table1]中删除所有用户，这些用户的[Table2]中的所有行都带有“open”列值＆lt; 1.我首先尝试选择它们，但它会产生SQL错误：

尝试1：

SELECT pg_acymailing_subscriber.*,
       COUNT(DISTINCT case when pg_acymailing_userstats.open > 0 end) as readc
LEFT JOIN `pg_acymailing_userstats`
    ON pg_acymailing_subscriber.subid=pg_acymailing_userstats.subid
WHERE pg_acymailing_subscriber.subid=24 AND readc > 0;

尝试2：

SELECT *
FROM `pg_acymailing_subscriber`
LEFT JOIN `pg_acymailing_userstats`
    ON pg_acymailing_subscriber.subid=pg_acymailing_userstats.subid
WHERE COUNT(DISTINCT case when pg_acymailing_userstats.open > 0 /*If user doesn't have rows with "open" column value > 0, we select it if whole rows numer is 0*/
                     end) < 1
  and pg_acymailing_subscriber.subid=24;

Answer 1

如果性能不是问题，那么使用子查询构建它可能是最容易的。

我对你的逻辑的理解是你要删除[Table1]中[Table2]中open > 0中没有任何行的所有用户，这是对你的要求的正确解释吗？

select * from pg_acymailing_subscriber where subid not in
( select subid from pg_acymailing_userstats where open > 0 )

如果显示正确的记录，请删除如下：

delete from pg_acymailing_subscriber where subid not in
( select subid from pg_acymailing_userstats where open > 0 )

Answer 2

如果要过滤聚合函数的结果，则需要GROUP BY和HAVING子句，例如

。

SELECT pg_acymailing_subscriber.userid,
       COUNT(DISTINCT case when pg_acymailing_userstats.open > 0 end) as readc
FROM `pg_acymailing_subscriber`
LEFT JOIN `pg_acymailing_userstats`
    ON pg_acymailing_subscriber.subid=pg_acymailing_userstats.subid
WHERE pg_acymailing_subscriber.subid=24
GROUP BY pg_acymailing_subscriber.userid
HAVING readc > 0;

我猜测用户ID列名为userid。我可能没有正确的引用，但这很容易修复。

HAVING readc > 0可能是也可能不是mysql中的正确语法。如果不是，请编写HAVING COUNT(DISTINCT case when pg_acymailing_userstats.open > 0 end) > 0

Answer 3

如果我正确理解你想要删除table1中与table2中的id相关的行，那么所有打开消息的总和是＆lt; 1
这应该是选择

  select table1.userID
  from table1 
  inner  join table2 on table1.userID = table2.userID 
  group by table1.userID
  havine sum(open)<1

然后您可以使用删除

  detele 
  from table1 
  inner  join table2 on table1.userID = table2.userID 
  group by table1.userID
  havine sum(open)<1

如何删除Table2中的行，表2中的WHERE的COUNT大于0？

3 个答案: