[英]SELECT MAX from one column with SUM and GROUP BY for another, without subqueries
Consider the following table. 请考虑下表。
+----+------+--------+-------------+---------------------+
| id | user | amount | description | paid_on |
+----+------+--------+-------------+---------------------+
| 1 | 1 | 200 | wire | 2017-09-01 15:45:52 |
| 2 | 2 | 200 | paypal | 2017-09-09 05:05:05 |
| 3 | 3 | 150 | cash | 2017-09-02 12:34:56 |
| 4 | 1 | 20 | wire | 2017-01-09 01:23:45 |
+----+------+--------+-------------+---------------------+
I'm trying to get the total payments for each user, and the last payment date for that same user. 我正在尝试获取每个用户的总付款以及该用户的最后付款日期。 For this, I'm using 为此,我正在使用
SELECT
user,
ROUND(SUM(amount),2) AS amount,
date_format(paid_on, '%d.%m.%Y.') AS paid_on
FROM
(
SELECT
user,
amount,
paid_on
FROM payments
WHERE paid_on BETWEEN '2017-09-01 00:00:00' AND '2017-09-30 23:59:59'
ORDER BY paid_on DESC
) tmppayments
GROUP BY user
It works as I expect it to, as it returns what I had in mind. 它按照我的预期工作,因为它返回了我的想法。 However, using a subquery seems like an overkill. 但是,使用子查询似乎有点矫枉过正。 Is it possible to do this with a simple(r) query, without resorting to any subqueries? 是否可以使用简单的(r)查询执行此操作,而无需借助任何子查询?
Would this do? 这会吗?
SELECT
user,
ROUND(SUM(amount),2) AS amount,
date_format(MAX(paid_on),'%d.%m.%Y.') AS paid_on
FROM
payments
GROUP BY user
Note that I left out the BETWEEN '2017-09-01 00:00:00' AND '2017-09-30 23:59:59'
condition because you never mentioned it as something you wanted. 请注意,我遗漏了BETWEEN '2017-09-01 00:00:00' AND '2017-09-30 23:59:59'
条件,因为你从来没有提到它是你想要的东西。
Use MAX
function to select the latest paid_on
date. 使用MAX
函数选择最新的paid_on
日期。
Query 询问
select `user`,
round(sum(`amount`),2) as `amount`,
date_format(max(`paid_on`), '%d.%m.%Y.') as `paid_on`
from `payments`
where `paid_on` between '2017-09-01 00:00:00' and '2017-09-30 23:59:59'
group by `user`;
Then just don't use a subquery : 然后就是不要使用子查询:
SELECT
user,
ROUND(SUM(amount),2) AS amount,
MAX(date_format(paid_on, '%d.%m.%Y.')) AS max_paid_on
FROM payments
WHERE paid_on BETWEEN '2017-09-01 00:00:00' AND '2017-09-30 23:59:59'
GROUP BY user
Though you should know that a sub query won't necessarily slow down your query, and in this case it probably won't 虽然您应该知道子查询不一定会减慢您的查询速度,在这种情况下它可能不会
Have you tried this way?: 你试过这种方式吗?:
SELECT user,
ROUND(SUM(amount),2) AS amount,
date_format(max(paid_on), '%d.%m.%Y.') AS paid_on
FROM payments
WHERE paid_on BETWEEN '2017-09-01 00:00:00' AND '2017-09-30 23:59:59'
GROUP BY user
You don't need the subquery at all. 您根本不需要子查询。 And, you can also simplify the date logic: 而且,您还可以简化日期逻辑:
SELECT p.user, SUM(p.amount) as total_amount, MAX(p.paid_on) as max_paid_on
FROM payments p
WHERE p.paid_on >= '2017-09-01' AND p.paid_on <'2017-10-01'
GROUP BY user
ORDER BY max_paid_on DESC;
Notes: 笔记:
max_paid_on
if you like. 如果您愿意,可以格式化max_paid_on
。 I much prefer the ISO standard format, YYYY-MM-DD, to any other. 我更喜欢ISO标准格式,YYYY-MM-DD,以及其他任何格式。 BETWEEN
with dates or date time columns. 我不建议将BETWEEN
与日期或日期时间列一起使用。 Here is a good blog post explaining why (although it is for SQL Server, it really applies to all databases). 这是一篇很好的博客文章,解释了为什么(尽管它适用于SQL Server,它确实适用于所有数据库)。 select
, paid_on
is not being aggregated and it is not in the group by
. 在外部select
, paid_on
未被聚合,并且不在group by
。 This would be an error in almost any other database. 这几乎是任何其他数据库中的错误。 SELECT
p.user,
ROUND(SUM(p.amount), 2) AS amount,
date_format(MAX(p.paid_on), '%d.%m.%Y.') AS paid_on
FROM
payments p
WHERE
p.paid_on BETWEEN '2017-09-01 00:00:00' AND '2017-09-30 23:59:59'
GROUP BY
p.user
ORDER BY
p.paid_on DESC
The subquery is unnecessarily added here. 子查询在此处被不必要地添加。 The best way to do it without the subquery is SELECT user, ROUND(SUM(amount),2) AS amount, date_format(max(paid_on), '%d.%m.%Y.') AS paid_on FROM payments WHERE paid_on BETWEEN '2017-09-01 00:00:00' AND '2017-09-30 23:59:59' GROUP BY user
Hope it helps. 没有子查询的最佳方法是SELECT user, ROUND(SUM(amount),2) AS amount, date_format(max(paid_on), '%d.%m.%Y.') AS paid_on FROM payments WHERE paid_on BETWEEN '2017-09-01 00:00:00' AND '2017-09-30 23:59:59' GROUP BY user
希望它SELECT user, ROUND(SUM(amount),2) AS amount, date_format(max(paid_on), '%d.%m.%Y.') AS paid_on FROM payments WHERE paid_on BETWEEN '2017-09-01 00:00:00' AND '2017-09-30 23:59:59' GROUP BY user
帮助。
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