Question

我有一张记录表，其中包含一个创建日期。我想返回过去6个日历月中的每一个的新记录，包括本月的部分记录。我对SQL Server了如指掌，但对PostgreSQL并不熟悉。

我已经能够使用此查询获取滚动月份的数据：

select 
COUNT(ID) as Total,
COUNT(CASE WHEN createddate between (now() - '1 month'::interval)::timestamp AND now() THEN AG.ID END) as ThisMonth,
COUNT(CASE WHEN createddate between (now() - '2 month'::interval)::timestamp AND (now() - '1 month'::interval)::timestamp THEN AG.ID END) as LastMonth,
COUNT(CASE WHEN createddate between (now() - '3 month'::interval)::timestamp AND (now() - '2 month'::interval)::timestamp THEN AG.ID END) as PrevMonth,
COUNT(CASE WHEN createddate between (now() - '4 month'::interval)::timestamp AND (now() - '3 month'::interval)::timestamp THEN AG.ID END) as PrevMonth2,
COUNT(CASE WHEN createddate between (now() - '5 month'::interval)::timestamp AND (now() - '4 month'::interval)::timestamp THEN AG.ID END) as PrevMonth3,
COUNT(CASE WHEN createddate between (now() - '6 month'::interval)::timestamp AND (now() - '5 month'::interval)::timestamp THEN AG.ID END) as PrevMonth4
FROM a_group AG

但是在6月21日，这将返回5 / 22-6 / 21,4 / 22-5 / 21等数据。我希望数据如下：6 / 1-6 / 21（部分当前月份），5 / 1-5 / 31等。

有什么建议吗？我也怀疑我可以在一个循环中做到这一点，但我还不熟悉语法。现在，我正在从PostgreSQL Maestro对备份文件进行测试。

感谢。

Answer 1

我认为date_trunc功能可能是您的朋友（请参阅postgres docs）。你会做这样的事情我猜：

select 
COUNT(ID) as Total,
COUNT(CASE WHEN createddate between date_trunc('month', now()) AND now() THEN AG.ID END) as ThisMonth,
COUNT(CASE WHEN createddate between date_trunc('month', now()) - interval '1 month' AND date_trunc('month', now()) - interval '1 day' THEN AG.ID END) as LastMonth,

等...

在PostgreSQL中查找过去n个月中每个月的新记录

1 个答案: