Question

对于SQL Server，我有一个带

的表

CostumerID  TITLE   DATE
1   m1  1999-05-08
1   m1  2000-07-10
1   m1  2001-12-11
1   m2  2008-03-20
1   m2  2005-09-05
1   m2  2011-07-08
1   m3  2006-07-22
1   m3  2009-01-19
1   m3  2012-02-18
2   m1  2007-09-28
2   m1  2010-11-19
2   m1  2009-08-09
2   m2  2010-04-22
2   m2  2008-10-16
2   m2  2010-07-22
2   m3  2013-07-31
2   m3  2011-01-11
2   m3  2010-02-20
3   m1  2010-04-07
3   m1  2011-06-11
3   m1  2010-11-09
3   m2  2013-08-21
3   m2  2014-07-19
3   m2  2015-12-29
3   m3  2011-04-17
3   m3  2014-01-31
3   m3  2012-09-19
2   m3  2010-02-03
…

问题1：我需要找到1月和2月消费了产品的CostumerID。

Select a.CostumerID  
From 
(Select distinct CostumerID  from theTable  where month(date) = '2') as a
Inner join 
(Select distinct CostumerID  from theTable where month(date) = '1') as b
On a.CostumerID  = b.CostumerID

Q2：另外，我需要找到每个客户第一次消费的所有产品中最喜欢的产品。

Select b.title, count(b.title) as cnt
from
(
Select a.CostumerID , min(a.date) as earliestDate
from [DJX_test1].dbo.ama_services  as a 
group by a.CostumerID 
) as c
inner join [DJX_test1].dbo.ama_services  as b
on b.CostumerID = c.CostumerID and b.[date] = c.earliestDate
group by b.title
order by cnt desc

表格大小可能很大，有10多万行。没有使用子查询会有更好的查询吗？另外，如何在不运行查询的情况下估计查询的性能？

感谢

Answer 1

对于第一个问题，试试这个：

SELECT DISTINCT costumerID
FROM theTable
WHERE month(date)='1' OR month(date)='2'

Answer 2

问题1：我需要找到1月和2月消费了产品的CostumerID。

SELECT costumerID
FROM theTable
WHERE month(Convert(date,[date]))='1' OR month(Convert(date,[date]))='2'

Q2：另外，我需要找到每个客户第一次消费的所有产品中最喜欢的产品。

您可以使用如下的dense_rank（）函数轻松实现它。

;with cte as
(
    select costumerID,title,date,
    dense_rank() over (partition by costumerid order by convert(Date,[date])) as rn
    from theTable
)
select * from cte where rn=1

从SQL服务器上的大表中查找最喜欢的产品

2 个答案: