[英]how to find the difference between last two entries in Mysql
我需要一個關於 MySQL 中最后兩個條目差異之間的差異的解決方案
SELECT DATE_FORMAT(order_datetime,'%m/%Y') as date,
SUM(order_total_after_tax) as number
FROM tbl_order
WHERE status = 'Confirmed'
GROUP BY DATE_FORMAT(order_datetime,'%Y/%m')
Limit 2
輸出 :
date number
02/2019 2345.01
03/2019 103751.05
但我需要一個確切的解決方案是我需要找到最后兩個結果之間的差異
2345.01 -103751.05
結果: -101406.04
在 MySQL 中如何做 Query 是什么?
你可以試試交叉連接
select a.date, a.number, b.number, a.number - b.number my_diff
from (
SELECT DATE_FORMAT(order_datetime,'%m/%Y') as date
, SUM(order_total_after_tax) as number
FROM tbl_order
where status='Confirmed'
GROUP BY DATE_FORMAT(order_datetime,'%Y/%m')
Limit 2
) a
CROSS JOIN (
SELECT DATE_FORMAT(order_datetime,'%m/%Y') as date
, SUM(order_total_after_tax) as number
FROM tbl_order
where status='Confirmed'
GROUP BY DATE_FORMAT(order_datetime,'%Y/%m')
) b ON a.date = b.date and a.number <> b.number
一種方法是cross join
,但它看起來像這樣:
SELECT last.number - last_1.number
FROM (SELECT DATE_FORMAT(order_datetime,'%m/%Y') as date,
SUM(order_total_after_tax) as number
FROM tbl_order
WHERE status = 'Confirmed'
GROUP BY DATE_FORMAT(order_datetime,'%Y/%m')
ORDER BY date
LIMIT 1
) as last CROSS JOIN
(SELECT DATE_FORMAT(order_datetime,'%m/%Y') as date,
SUM(order_total_after_tax) as number
FROM tbl_order
WHERE status = 'Confirmed'
GROUP BY DATE_FORMAT(order_datetime,'%Y/%m')
ORDER BY date
LIMIT 1 OFFSET 1
) last_1
SELECT last.number - last_1.number FROM (SELECT DATE_FORMAT(order_datetime,'%m/%Y') as date, SUM(order_total_after_tax) as number FROM tbl_order WHERE status = 'Confirmed' GROUP BY DATE_FORMAT(order_datetime,'%Y/%m') ORDER BY date DESC LIMIT 1 ) as last CROSS JOIN (SELECT DATE_FORMAT(order_datetime,'%m/%Y') as date, SUM(order_total_after_tax) as number FROM tbl_order WHERE status = 'Confirmed' GROUP BY DATE_FORMAT(order_datetime,'%Y/%m') ORDER BY date DESC LIMIT 1 OFFSET 1 ) last_1
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