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 |
+----+------+--------+-------------+---------------------+
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。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
它按照我的预期工作,因为它返回了我的想法。但是,使用子查询似乎有点矫枉过正。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?
答案 0 :(得分:2)
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
请注意,我遗漏了BETWEEN '2017-09-01 00:00:00' AND '2017-09-30 23:59:59'
条件,因为您从未将其视为您想要的内容。
答案 1 :(得分:2)
使用MAX
功能选择最新的paid_on
日期。
<强>查询强>
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`;
答案 2 :(得分:2)
然后不要使用子查询:
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
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,它可能会赢得
答案 3 :(得分:2)
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
答案 4 :(得分:2)
根本不需要子查询。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;
注意:
max_paid_on
。我更喜欢ISO标准格式,YYYY-MM-DD,以及其他任何格式。BETWEEN
与日期或日期时间列一起使用。 Here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
未被汇总,而且不在group by
中。这几乎是任何其他数据库中的错误。 答案 5 :(得分:2)
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
答案 6 :(得分:1)
此处不必要地添加子查询。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
希望能帮助到你。