[英]SQL- return a difference of number in a column in a table grouped by year (ORACLE)
我有兩個表,如下所示:
資產表:
assetnum | depid
----------------
1 | eng
2 | ap
3 | cao
. | .
. | .
. | .
和
抄表:
assetnum | meterreading_date | reading
---------------------------------------
1 | 4/7/2017 | 50000
2 | 3/5/17 | 30000
3 | 1/15/17 | 10000
. | . | .
. | . | .
. | . | .
我正在努力加入並獲得每種資產的年度使用量。 換句話說,我想獲取資產編號depid(按當年使用情況分組)(該年記錄的最后日期的最后一次讀數-該年記錄的第一個日期的第一次讀數)。
例如在上述情況下,我將輸出為
assetnum | depid | usage
-------------------------
1 | eng | 40000 (50000-10000)
. | . | .
. | . | .
. | . | .
如果我理解正確,則只需要join
和group by
:
select mr.assetnum, a.depid,
(max(usage) - min(usage)) as usage
from Meterreading mr join
Asset a
on mr.assetnum = a.assetnum
where meterreading_date >= date '2017-01-01 and
meterreading_date < '2018-01-01' -- unnecessary for the current year
group by mr.assetnum, a.depid;
Tweeking Gordon的回答...只是從日期中提取年份,然后根據其分組以消除位置。
SELECT mr.assetnum
, a.depid
, max(usage) - min(usage) as usage
, to_char(meterreading_date,'YYYY') as Year
FROM Meterreading mr
INNER join Asset a
on mr.assetnum = a.assetnum
GROUP BY mr.assetnum, a.depid, to_char(meterreading_date,'YYYY')
或者...使用解壓縮vs to_char ...
SELECT mr.assetnum
, a.depid
, max(usage) - min(usage) as usage
, extract(year from meterreading_date) as Year
FROM Meterreading mr
INNER join Asset a
on mr.assetnum = a.assetnum
GROUP BY mr.assetnum, a.depid, extract(year from meterreading_date)
在這兩種情況下,這都會獲得每年的MIN(最小)和max(最大)使用量,並從最大值中減去最小。 它不是日期驅動的,而是使用/年驅動的。 如果您出於某種原因在當年晚些時候的讀數低於最高值...它可能無法返回預期的結果...要真正成為日期驅動型,我們需要獲取最小/最大日期來查找這些值的用法並從那里去。
例如,如果閱讀是:
assetnum | meterreading_date | reading
---------------------------------------
1 | 7/5/2017 | 70000
1 | 6/1/2017 | 10000
1 | 5/7/2017 | 60000
1 | 4/7/2017 | 50000
1 | 3/5/17 | 30000
1 | 1/15/17 | 20000
那么2017年資產編號1的使用量為70000-10000或60000; 但也許您想要70000-20000 = 50000 ...
按年份分組的另一個答案:
SELECT reading.*, max_reading-min_reading used, depid
FROM
( SELECT TRUNC(meterreading_date,'yyyy') meterreading_date, assetnum, MIN(reading) min_reading, MAX(reading) max_reading
FROM METERREADING
GROUP BY TRUNC(meterreading_date,'yyyy'), assetnum
) reading
JOIN
asset ON asset.assetnum=reading.assetnum
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