有没有办法在SQL Server中编写这样的查询，而不使用select两次然后加入？
select trans_date, datepart(HOUR,trans_time) as hour,
(datepart(MINUTE,trans_time)/30)*30 as minute,
case
when paper_number = 11111/*paperA*/
then sum(t1.price*t1.amount)/SUM(t1.amount)*100
end as avgA,
case
when paper_number = 22222/*PaperB*/
then sum(t1.price*t1.amount)/SUM(t1.amount)*100
end as avgB
from dbo.transactions t1
where trans_date = '2006-01-01' and (paper_number = 11111 or paper_number = 22222)
group by trans_date, datepart(HOUR,trans_time), datepart(MINUTE,trans_time)/30
order by hour, minute
SQL Server要求我将paper_number添加到group by，并在我这样做时返回null
trans_date hour minute avgA avgB
2006-01-01 9 30 1802.57199725463 NULL
2006-01-01 9 30 NULL 169125.886524823
2006-01-01 10 0 1804.04742534103 NULL
2006-01-01 10 0 NULL 169077.777777778
2006-01-01 10 30 1806.18773535637 NULL
2006-01-01 10 30 NULL 170274.550381867
2006-01-01 11 0 1804.43466045433 NULL
2006-01-01 11 0 NULL 170743.4
2006-01-01 11 30 1807.04532012137 NULL
2006-01-01 11 30 NULL 171307.00280112
答案 0 :(得分：3)
对整个CASE表达式使用SUM（）函数
select trans_date, datepart(HOUR,trans_time) as hour, (datepart(MINUTE,trans_time)/30)*30 as minute,
sum(case when paper_number = 11111/*paperA*/ then t1.price*t1.amount end) * 1.00
/ sum(case when paper_number = 11111/*paperA*/ then t1.amount end) * 100 as avgA,
sum(case when paper_number = 22222/*PaperB*/ then t1.price*t1.amount end) * 1.00
/ sum(case when paper_number = 22222/*paperB*/ then t1.amount end) * 100 as avgB
from dbo.transactions t1
where trans_date = '2006-01-01'
group by trans_date, datepart(HOUR,trans_time), datepart(MINUTE,trans_time)/30
order by hour, minute
SQLFiddle上的演示
答案 1 :(得分：3)
尝试：
with cte as
(select trans_date,
datepart(HOUR,trans_time) as hour,
(datepart(MINUTE,trans_time)/30)*30 as minute,
sum(case when paper_number = 11111/*paperA*/
then t1.price*t1.amount else 0 end) as wtdSumA,
sum(case when paper_number = 11111/*paperA*/
then t1.amount else 0 end) as amtSumA,
sum(case when paper_number = 22222/*PaperB*/
then t1.price*t1.amount else 0 end) as wtdSumB,
sum(case when paper_number = 22222/*PaperB*/
then t1.amount else 0 end) as amtSumB
from dbo.transactions t1
where trans_date = '2006-01-01'
group by trans_date, datepart(HOUR,trans_time), datepart(MINUTE,trans_time)/30)
select trans_date, hour, minute,
case amtSumA when 0 then 0 else 100 * wtdSumA / amtSumA end as avgA,
case amtSumB when 0 then 0 else 100 * wtdSumB / amtSumB end as avgB
from cte
order by hour, minute
（SQLFiddle here）
你可以在没有CTE的情况下得出这个，如下：
select trans_date,
datepart(HOUR,trans_time) as hour,
(datepart(MINUTE,trans_time)/30)*30 as minute,
case sum(case when paper_number = 11111/*paperA*/ then t1.amount else 0 end)
when 0 then 0
else 100 * sum(case when paper_number = 11111 then t1.price*t1.amount else 0 end)
/ sum(case when paper_number = 11111 then t1.amount else 0 end) end as avgA,
case sum(case when paper_number = 22222/*paperA*/ then t1.amount else 0 end)
when 0 then 0
else 100 * sum(case when paper_number = 22222 then t1.price*t1.amount else 0 end)
/ sum(case when paper_number = 22222 then t1.amount else 0 end) end as avgB
from dbo.transactions t1
where trans_date = '2006-01-01'
group by trans_date, datepart(HOUR,trans_time), datepart(MINUTE,trans_time)/30
order by 1,2,3
答案 2 :(得分：2)
您也可以尝试使用UNPIVOT和PIVOT，如下所示：
WITH prepared AS (
SELECT
trans_date,
trans_time = DATEADD(MINUTE, DATEDIFF(MINUTE, '00:00', trans_time) / 30 * 30, CAST('00:00' AS time)),
paper_number,
total = price * amount,
amount
FROM transactions
),
unpivoted AS (
SELECT
trans_date,
trans_time,
attribute = attribute + CAST(paper_number AS varchar(10)),
value
FROM prepared
UNPIVOT (value FOR attribute IN (total, amount)) u
),
pivoted AS (
SELECT
trans_date,
trans_time,
avgA = total11111 * 100 / amount11111,
avgB = total22222 * 100 / amount22222
FROM unpivoted
PIVOT (
SUM(value) FOR attribute IN (total11111, amount11111, total22222, amount22222)
) p
)
SELECT *
FROM pivoted
;
为了解释上述查询的工作原理，下面是对原始数据集在查询执行过程中经历的转换的描述，使用以下示例：
trans_date trans_time paper_number price amount
---------- ---------- ------------ ----- ------
2013-04-09 11:12:35 11111 10 15
2013-04-09 11:13:01 22222 24 10
2013-04-09 11:28:44 11111 12 5
2013-04-09 11:36:20 22222 20 11
prepared CTE生成以下列集：
trans_date trans_time paper_number total amount
---------- ---------- ------------ ----- ------
2013-04-09 11:00:00 11111 150 15
2013-04-09 11:00:00 22222 240 10
2013-04-09 11:00:00 11111 60 5
2013-04-09 11:30:00 22222 220 11
其中trans_time为原始trans_time向下舍入到最近的半小时，total为price乘以amount。
unpivoted CTE忽略了total和amount值，以生成attribute和value：
trans_date trans_time paper_number attribute value
---------- ---------- ------------ --------- -----
2013-04-09 11:00:00 11111 total 150
2013-04-09 11:00:00 11111 amount 15
2013-04-09 11:00:00 22222 total 240
2013-04-09 11:00:00 22222 amount 10
2013-04-09 11:00:00 11111 total 60
2013-04-09 11:00:00 11111 amount 5
2013-04-09 11:30:00 22222 total 220
2013-04-09 11:30:00 22222 amount 11
然后paper_number与attribute合并形成一个列，也称为attribute：
trans_date trans_time attribute value
---------- ---------- ----------- -----
2013-04-09 11:00:00 total11111 150
2013-04-09 11:00:00 amount11111 15
2013-04-09 11:00:00 total22222 240
2013-04-09 11:00:00 amount22222 10
2013-04-09 11:00:00 total11111 60
2013-04-09 11:00:00 amount11111 5
2013-04-09 11:30:00 total22222 220
2013-04-09 11:30:00 amount22222 11
最后，pivoted CTE将value数据转发回来，并使用SUM()并使用attribute列名称进行聚合：
trans_date trans_time total11111 amount11111 total22222 amount22222
---------- ---------- ---------- ----------- ---------- -----------
2013-04-09 11:00:00 210 20 240 10
2013-04-09 11:30:00 NULL NULL 220 11
然后另外处理旋转的值（每totalNNN乘以100并除以相应的amountNNN）以形成最终输出：
trans_date trans_time avgA avgB
---------- ---------- ---- ----
2013-04-09 11:00:00 1050 2400
2013-04-09 11:30:00 NULL 2000
可能需要解决几个问题：
如果price和amount是不同的数据类型，则total和amount也可能会以不同的数据类型结束。对于UNPIVOT，要取消隐藏的值必须具有完全相同的类型，因此您需要将total和amount的显式转换添加到一些常见的类型，可能会阻止数据/精度损失。这可以在这样的prepared CTE中完成（假设共同类型为decimal(10,2)）：
total = CAST(price * amount AS decimal(10,2)),
amount = CAST(amount AS decimal(10,2))
如果汇总金额可能最终为0，那么您需要将除以0的问题考虑在内。一种方法可以是用NULL替换0量，这也会使除法的结果为NULL。将ISNULL或COALESCE应用于该结果将允许您将其转换为某个默认值，例如0。因此，在pivoted CTE：
avgA = ISNULL(total11111 * 100 / NULLIF(amount11111, 0), 0),
avgB = ISNULL(total22222 * 100 / NULLIF(amount22222, 0), 0)