仅选择重复

Question

On Top是一个示例数据库。我需要一个查询来显示

1. 过滤一次持续制作多个项目的客户。
2. 删除当前没有正在进行的项目的任何客户的记录（应删除过去项目的记录）。

请帮忙

GROUP BY CustomerID
Having COUNT(*) >= 1 is not working

Answer 1

对于重复项，有不同的技术，例如，您可以使用窗口功能：

;with cte as (
    select *, count(*) over(partition by customerID) as cnt
    from <Table>
)
select *
from cte
where
    cnt > 1

Answer 2

要仅获取最新项目，请使用row_number()：

with t as (
     select t.*,
            row_number() over (partition by customerid order by enddate desc) as seqnum
     from table t
    )
select t.*
from t
where seqnum > 1;

要从数据库中实际删除旧记录，可以使用类似的构造：

with todelete as (
     select t.*,
            row_number() over (partition by customerid order by enddate desc) as seqnum
     from table t
    )
delete from todelete
where seqnum = 1;

但是，如果您只是希望客户没有正在进行的项目：

select customerid
from table t
group by customerid
having sum(case when getdate() between startdate and endate then 1 else 0 end) = 0;