LeetCode：Database 68.每月交易II

Posted 2021-06-26 Xiao Miao

要求：编写一个 SQL 查询，以查找每个月和每个国家/地区的信息：已批准交易的数量及其总金额、退单的数量及其总金额。

注意：在您的查询中，只需显示给定月份和国家，忽略所有为零的行。

Transactions 记录表的结构：

+----------------+---------+
| Column Name    | Type    |
+----------------+---------+
| id             | int     |
| country        | varchar |
| state          | enum    |
| amount         | int     |
| trans_date     | date    |
+----------------+---------+
id 是这个表的主键。
该表包含有关传入事务的信息。
状态列是类型为 [approved（已批准）、declined（已拒绝）] 的枚举。

Chargebacks 表的结构：

+----------------+---------+
| Column Name    | Type    |
+----------------+---------+
| trans_id       | int     |
| trans_date     | date    |
+----------------+---------+
退单包含有关放置在事务表中的某些事务的传入退单的基本信息。
trans_id 是 transactions 表的 id 列的外键。
每项退单都对应于之前进行的交易，即使未经批准。

Transactions 表：

+-----+---------+----------+--------+------------+
| id  | country | state    | amount | trans_date |
+-----+---------+----------+--------+------------+
| 101 | US      | approved | 1000   | 2019-05-18 |
| 102 | US      | declined | 2000   | 2019-05-19 |
| 103 | US      | approved | 3000   | 2019-06-10 |
| 104 | US      | declined | 4000   | 2019-06-13 |
| 105 | US      | approved | 5000   | 2019-06-15 |
+-----+---------+----------+--------+------------+

Chargebacks Table：

+----------+------------+
| trans_id | trans_date |
+----------+------------+
| 102      | 2019-05-29 |
| 101      | 2019-06-30 |
| 105      | 2019-09-18 |
+----------+------------+

Result Table：

+---------+---------+----------------+-----------------+------------------+-------------------+
| month   | country | approved_count | approved_amount | chargeback_count | chargeback_amount |
+---------+---------+----------------+-----------------+------------------+-------------------+
| 2019-05 | US      | 1              | 1000            | 1                | 2000              |
| 2019-06 | US      | 2              | 8000            | 1                | 1000              |
| 2019-09 | US      | 0              | 0               | 1                | 5000              |
+---------+---------+----------------+-----------------+------------------+-------------------+

SQL语句：

with c as(
select substr(a.trans_date,1,7) as month,b.country,count(a.trans_id) as chargeback_count,sum(b.amount) as chargeback_amount
from Chargebacks a
join  Transactions b
on a.trans_id=b.id
group by b.country,substr(a.trans_date,1,7))
,
d as(select substr(trans_date,1,7) as month,country,count(id) as approved_count,sum(amount) as approved_amount
from  Transactions
where state="approved"
group by country,substr(trans_date,1,7)
),f as( 
select distinct month,country from(
select month,country
from c
union all
select month,country
from d)e)


select f.month,f.country,ifnull(d.approved_count,0) as approved_count,ifnull(d.approved_amount,0) as approved_amount,
ifnull(c.chargeback_count,0) as chargeback_count,ifnull(c.chargeback_amount,0) as chargeback_amount
from f
left join d
on f.month=d.month and f.country=d.country
left join c 
on f.month=c.month and f.country=c.country
order by f.month asc;