Question

我希望每次执行此语句时都不插入数据。它应该只能每天有效地插入一次数据。多数民众赞成我想要这样做。我的逻辑在这里有什么问题吗？我正在使用date(now())，因此它会插入今天的日期。我需要这是一个幂等插入。

INSERT INTO newsletter_subscription_counts
          (query_date, community_id, mailing_list, subscription_count)
  SELECT date(now()), a.community_id, 
     a.newsletter_type::mail_list_types, 
     count(a.subscriber_user_id)
   FROM
      newsletter_subscribers_main a
   LEFT OUTER JOIN newsletter_subscription_counts b
   ON (a.community_id = b.community_id)
   AND (a.newsletter_type::mail_list_types = b.mailing_list)
   AND (a.created_at = b.query_date)
   WHERE b.query_date is null
   AND   b.mailing_list is null
GROUP BY a.community_id, a.newsletter_type, a.created_at

Answer 1

INSERT INTO newsletter_subscription_counts
      (query_date, community_id, newsletter_t, subscription_count)     
SELECT now()::date
      ,a.community_id
      ,a.newsletter_type
      ,count(*)
FROM   newsletter_subscribers_main a
LEFT   JOIN newsletter_subscription_counts b
                     ON  a.community_id = b.community_id
                     AND a.newsletter_type::mail_list_types = b.mailing_list
                     AND a.created_at = b.query_date
WHERE  a.created_at::date = now()::date
AND    b.query_date is null
GROUP  BY a.community_id, a.newsletter_type;

删除了一些噪音，改进了格式，最重要的是添加了WHERE子句：

WHERE  a.created_at::date = now()::date

如果created_at已经输入date，则不需要演员。

还要考虑我对你上一个问题的回答，我已经猜到了你的问题：
Need help understanding a complex query with multiple join conditions

只是，我在那里的猜测照顾了尚未插入的所有日子（并且更适合IMO）。

幂等INSERT无法按预期工作。我的查询逻辑有问题吗？

1 个答案: