SQL:选择组中包含的行

Question

我正在研究SQL Server的查询,我想知道是否有人可以给我一些关于选择构成组的单个行的提示(其中组基于聚合函数,在这种情况下为COUNT)

因此,作为一个简化的例子,如果我有一个账单表,如下所示,我想为每个客户选择在特定日期之后有2个或更多账单的所有账单.

ClaimID     ClaimDate             ClientName
101         May 5, 2010           Jim
102         June 19, 2010         Jim
103         August 5, 2008        Jim
104         January 1, 2011       Mary
105         May 8, 2009           Mary
106         November 4, 2010      Mary
107         October 6, 2010       Mary
108         April 4, 2010         Bob
109         April 29, 2009        Bob
110         July 7, 2006          Joe

所以,如果我执行

SELECT ClientName, COUNT(ClaimID) FROM Billings
WHERE ClaimDate > '2010'
Group By ClientName
Having COUNT(ClaimID) > 1

我得到:

Jim  2
Mary    3

哪个好,它找到所有在时间范围内有2个或更多账单的客户,但我想列出那些账单是什么.所以我想要这个:

ClaimID ClientName  Count
101         Jim     2
102         Jim     2
104         Mary    3
106         Mary    3
107         Mary    3

您认为实现这一目标的最佳方式是什么？

谢谢.

Answer 1

您将其加入主表.

SELECT B.ClaimID, B.ClaimDate, B.ClientName, G.ClaimCount
FROM
(
    SELECT ClientName, COUNT(ClaimID) ClaimCount
    FROM Billings
    WHERE ClaimDate > '2010'
    Group By ClientName
    Having COUNT(ClaimID) > 1
) G
INNER JOIN Billings B on B.ClientName = G.ClientName
WHERE B.ClaimDate > '2010'

Answer 2

假设 SQL Server 2005 或更高版本可以使用公用表表达式

With MultipleBillings As
    (
    Select ClaimId, ClaimDate, ClientName
        , Count(ClaimId) Over ( Partition By ClientName ) As BillingCount
    From Billings
    Where ClaimDate > '2010'
    )
Select ClaimId, ClaimDate, ClientName
From MultipleBillings
Where BillingCount > 1