我似乎有一个作家阻止的时刻。
我需要一个查询，该查询将在特定日期按客户和帐户返回最大付款。
2 个表，其中一个用于客户和客户数据（客户 1 有 50 个客户），第二个表用于接收付款和日期。
所以我想要一个显示的表格：
Client | Account | Paid | Date
----------------------------------------
1 | 1234 | £2.99 | 01/11/2012
2 | 1235 | £4.99 | 08/12/2012
希望这是有道理的！在我的脑海里它应该很简单！
谢谢
这个问题很有趣。使用聚合查询解决了这个问题。
SQL 小提琴：http ://www.sqlfiddle.com/#!3/29256/1/0
select d.[Client], c.[Account],
max([Paid])as 'PAID',
d.[Date]
from Customer c, Data d where
d.[Client] = c.[Client]
group by d.[Client],c.[Account],d.[Date];
产生结果：
CLIENT ACCOUNT PAID DATE
1 Stack 123 January, 01 2013 00:00:00+0000
1 Stack 234 January, 02 2013 00:00:00+0000
1 Stack 33 January, 03 2013 00:00:00+0000
2 Over 674 January, 04 2013 00:00:00+0000
2 Over 2424 January, 05 2013 00:00:00+0000
2 Over 4545 January, 06 2013 00:00:00+0000
3 Flow 22 January, 07 2013 00:00:00+0000
3 Flow 3456 January, 08 2013 00:00:00+0000
3 Flow 445 January, 09 2013 00:00:00+0000
如果我们遇到客户可能拥有多个帐户的情况，并且我们想找到在特定日期支付的最大金额的客户帐户，我们将不得不做一些更复杂的事情：
select *
from Customer c2, Data d2,
(
select d.[Client],
max([Paid])as 'PAID',
d.[Date]
from Customer c,
Data d
where
d.[Client] = c.[Client] group by d.[Client],d.[Date]
) subQ
where c2.[client] = d2.[client] and
c2.[client] = subQ.[client] and
d2.[Paid] = subQ.[Paid] and
d2.[Date] = subQ.[Date];
由于您无法将其他列添加到不属于 group by 的查询中 - 请参阅：http ://technicalsmile.blogspot.gr/2011/04/column-is-invalid-in-select-list.html
select
Customer.name,
Account.name as account_name,
[date],
max(paid)
from Data,
Customer,
Account
where Data.client = Customer.id
and Data.account = Account.id
group by Customer.name, Account.name, [date]
SQL Server 支持Common Table Expression和Windowing Function. 查询使用DENSE_RANK()根据最大Paid为每个给出排名值Account。所以第一个值是最大值，排名值为1。这是您要过滤的值。
假设链接两个表的列是Client
WITH record
AS
(
SELECT a.Client, a.Account, b.Paid, b.Date,
DENSE_RANK() OVER (PARTITION BY a.Client ORDER BY b.Paid DESC) rn
FROM Customer a
INNER JOIN Data b
ON a.Client = b.Client
)
SELECT Client, Account, Paid, Date
FROM record
WHERE rn = 1
考虑以下记录（来自SQLFiddle Demo）
客户表
╔════════╦═════════╗
║ CLIENT ║ ACCOUNT ║
╠════════╬═════════╣
║ 1 ║ Stack ║
║ 2 ║ Over ║
║ 3 ║ Flow ║
╚════════╩═════════╝
数据表
╔════════╦══════╦════════════════════════════════╗
║ CLIENT ║ PAID ║ DATE ║
╠════════╬══════╬════════════════════════════════╣
║ 1 ║ 123 ║ January, 01 2013 00:00:00+0000 ║
║ 1 ║ 234 ║ January, 02 2013 00:00:00+0000 ║
║ 1 ║ 33 ║ January, 03 2013 00:00:00+0000 ║
║ 2 ║ 674 ║ January, 04 2013 00:00:00+0000 ║
║ 2 ║ 2424 ║ January, 05 2013 00:00:00+0000 ║
║ 2 ║ 4545 ║ January, 06 2013 00:00:00+0000 ║
║ 3 ║ 22 ║ January, 07 2013 00:00:00+0000 ║
║ 3 ║ 3456 ║ January, 08 2013 00:00:00+0000 ║
║ 3 ║ 445 ║ January, 09 2013 00:00:00+0000 ║
╚════════╩══════╩════════════════════════════════╝
连接表的结果
╔════════╦═════════╦══════╦════════════════════════════════╗
║ CLIENT ║ ACCOUNT ║ PAID ║ DATE ║
╠════════╬═════════╬══════╬════════════════════════════════╣
║ 1 ║ Stack ║ 123 ║ January, 01 2013 00:00:00+0000 ║
║ 1 ║ Stack ║ 234 ║ January, 02 2013 00:00:00+0000 ║ << Expected Output
║ 1 ║ Stack ║ 33 ║ January, 03 2013 00:00:00+0000 ║
║ 2 ║ Over ║ 674 ║ January, 04 2013 00:00:00+0000 ║
║ 2 ║ Over ║ 2424 ║ January, 05 2013 00:00:00+0000 ║
║ 2 ║ Over ║ 4545 ║ January, 06 2013 00:00:00+0000 ║ << Expected Output
║ 3 ║ Flow ║ 22 ║ January, 07 2013 00:00:00+0000 ║
║ 3 ║ Flow ║ 3456 ║ January, 08 2013 00:00:00+0000 ║ << Expected Output
║ 3 ║ Flow ║ 445 ║ January, 09 2013 00:00:00+0000 ║
╚════════╩═════════╩══════╩════════════════════════════════╝
最终输出
╔════════╦═════════╦══════╦════════════════════════════════╗
║ CLIENT ║ ACCOUNT ║ PAID ║ DATE ║
╠════════╬═════════╬══════╬════════════════════════════════╣
║ 1 ║ Stack ║ 234 ║ January, 02 2013 00:00:00+0000 ║
║ 2 ║ Over ║ 4545 ║ January, 06 2013 00:00:00+0000 ║
║ 3 ║ Flow ║ 3456 ║ January, 08 2013 00:00:00+0000 ║
╚════════╩═════════╩══════╩════════════════════════════════╝