如何（MySQL）乘以列然后求和行？
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时间：2020-08-31 18:16:28 来源:igfitidea点击:
How to (MySQL) multiply columns and then the sum rows?
提问by trafalgar
I've got this table:
我有这张桌子：
id | payment_id | quantity | unit cost
1 633 1 750
2 633 1 750
3 632 2 750
4 632 2 750
What I need is :
我需要的是：
payemnt_id | total
633 1500
632 3000
You can also think of this as Countries and then you are trying to find the total for each Country. I was sure there were some tutorials like this but could not find by STFW.
您也可以将其视为国家，然后您试图找到每个国家的总数。我确信有一些这样的教程，但 STFW 找不到。
回答by lc.
You can simply put the formula (expression) inside SUM:
你可以简单地把公式（表达式）放在里面SUM：
SELECT payment_id, SUM(`unit cost` * quantity) AS total
FROM myTable
GROUP BY payment_id
回答by Maxim Zhukov
SELECT payemnt_id, SUM(`unit cost` * quantity) as total
FROM Table1
GROUP BY payemnt_id
回答by AmazingDreams
SELECT
payment_id,
SUM(subtotal) AS total
FROM(
SELECT
payment_id,
(unit_cost * quantity) AS subtotal
) AS t1
GROUP BY
payment_id
