描述：
表：Accounts +----------------+------+ | Column Name | Type | +----------------+------+ | account_id | int | | max_income | int | +----------------+------+ account_id 是这张表具有唯一值的列。 每行包含一个银行账户每月最大收入的信息。表：Transactions
+----------------+----------+ | Column Name | Type | +----------------+----------+ | transaction_id | int | | account_id | int | | type | ENUM | | amount | int | | day | datetime | +----------------+----------+ transaction_id 是这张表具有唯一值的列。 每行包含一条转账信息。 type 是枚举类型（包含'Creditor','Debtor'），其中 'Creditor' 表示用户向其账户存入资金，'Debtor' 表示用户从其账户取出资金。 amount 是交易过程中的存入/取出的金额。如果一个账户在 连续两个及以上 月份的 总收入 超过最大收入（
max_income），那么认为这个账户 可疑。 账户当月 总收入 是当月存入资金总数（即 transactions 表中 type 字段的'Creditor'）。编写一个解决方案，报告所有的 可疑 账户。
以 任意顺序 返回结果表
返回结果格式如下示例所示。
示例 1:
输入： Accounts 表: +------------+------------+ | account_id | max_income | +------------+------------+ | 3 | 21000 | | 4 | 10400 | +------------+------------+ Transactions 表: +----------------+------------+----------+--------+---------------------+ | transaction_id | account_id | type | amount | day | +----------------+------------+----------+--------+---------------------+ | 2 | 3 | Creditor | 107100 | 2021-06-02 11:38:14 | | 4 | 4 | Creditor | 10400 | 2021-06-20 12:39:18 | | 11 | 4 | Debtor | 58800 | 2021-07-23 12:41:55 | | 1 | 4 | Creditor | 49300 | 2021-05-03 16:11:04 | | 15 | 3 | Debtor | 75500 | 2021-05-23 14:40:20 | | 10 | 3 | Creditor | 102100 | 2021-06-15 10:37:16 | | 14 | 4 | Creditor | 56300 | 2021-07-21 12:12:25 | | 19 | 4 | Debtor | 101100 | 2021-05-09 15:21:49 | | 8 | 3 | Creditor | 64900 | 2021-07-26 15:09:56 | | 7 | 3 | Creditor | 90900 | 2021-06-14 11:23:07 | +----------------+------------+----------+--------+---------------------+ 输出： +------------+ | account_id | +------------+ | 3 | +------------+ 解释： 对于账户 3： - 在 2021年6月，用户收入为 107100 + 102100 + 90900 = 300100。 - 在 2021年7月，用户收入为 64900。 可见收入连续两月超过21000的最大收入，因此账户3列入结果表中。 对于账户 4： - 在 2021年5月，用户收入为 49300。 - 在 2021年6月，用户收入为 10400。 - 在 2021年7月，用户收入为 56300。 可见收入在5月与7月超过了最大收入，但6月没有。因为账户没有没有连续两月超过最大收入，账户4不列入结果表中。
数据准备：
Create table If Not Exists Accounts (account_id int, max_income int)
Create table If Not Exists Transactions (transaction_id int, account_id int, type ENUM('creditor', 'debtor'), amount int, day datetime)
Truncate table Accounts
insert into Accounts (account_id, max_income) values ('3', '21000')
insert into Accounts (account_id, max_income) values ('4', '10400')
Truncate table Transactions
insert into Transactions (transaction_id, account_id, type, amount, day) values ('2', '3', 'Creditor', '107100', '2021-06-02 11:38:14')
insert into Transactions (transaction_id, account_id, type, amount, day) values ('4', '4', 'Creditor', '10400', '2021-06-20 12:39:18')
insert into Transactions (transaction_id, account_id, type, amount, day) values ('11', '4', 'Debtor', '58800', '2021-07-23 12:41:55')
insert into Transactions (transaction_id, account_id, type, amount, day) values ('1', '4', 'Creditor', '49300', '2021-05-03 16:11:04')
insert into Transactions (transaction_id, account_id, type, amount, day) values ('15', '3', 'Debtor', '75500', '2021-05-23 14:40:20')
insert into Transactions (transaction_id, account_id, type, amount, day) values ('10', '3', 'Creditor', '102100', '2021-06-15 10:37:16')
insert into Transactions (transaction_id, account_id, type, amount, day) values ('14', '4', 'Creditor', '56300', '2021-07-21 12:12:25')
insert into Transactions (transaction_id, account_id, type, amount, day) values ('19', '4', 'Debtor', '101100', '2021-05-09 15:21:49')
insert into Transactions (transaction_id, account_id, type, amount, day) values ('8', '3', 'Creditor', '64900', '2021-07-26 15:09:56')
insert into Transactions (transaction_id, account_id, type, amount, day) values ('7', '3', 'Creditor', '90900', '2021-06-14 11:23:07')
分析：
①首先先将type为creditor的数据筛选出来，同时将日期拆分为年、月
select account_id,amount,year(day)as year,substr(day,6,2)as month from transactions where type = 'creditor' order by account_id,year,month
②将每个account_id对应的max_income关联起来 然后过滤 根据账户id、年月分组排名
with t1 as ( select account_id,amount,year(day)as year,substr(day,6,2)as month from transactions where type = 'creditor' order by account_id,year,month ) , t2 as( select t1.account_id,sum(amount)total,year,month,max_income from t1,accounts where t1.account_id = Accounts.account_id group by account_id, year, month,max_income order by account_id) select account_id,total,year,month,max_income,row_number() over (partition by account_id order by month)r1 from t2 where total > max_income
③用month-r1 如果数值相同 那么就是连续月份，同时求出相同数值的个数 并且过滤出大于等于2的即为连续两个月及以上
with t1 as ( select account_id,amount,year(day)as year,substr(day,6,2)as month from transactions where type = 'creditor' order by account_id,year,month ) , t2 as( select t1.account_id,sum(amount)total,year,month,max_income from t1,accounts where t1.account_id = Accounts.account_id group by account_id, year, month,max_income order by account_id) , t3 as ( select account_id,total,year,month,max_income,row_number() over (partition by account_id order by month)r1 from t2 where total > max_income) # , t4 as ( select account_id,year,(month-r1) as m2,count((month-r1)) as r3 from t3 group by account_id ,year,(month-r1) having (count((month-r1))) >=2
图解：
代码：
with t1 as (
select
account_id,amount,year(day)as year,substr(day,6,2)as month
from transactions where type = 'creditor'
order by account_id,year,month )
, t2 as(
select t1.account_id,sum(amount)total,year,month,max_income from t1,accounts
where t1.account_id = Accounts.account_id
group by account_id, year, month,max_income
order by account_id)
, t3 as (
select account_id,total,year,month,max_income,row_number() over (partition by account_id order by month)r1
from t2
where total > max_income)
, t4 as (
select account_id,year,(month-r1) as m2,count((month-r1)) as r3
from t3
group by account_id ,year,(month-r1))
select distinct account_id from t4
where r3 >=2
;总结：
将日拆解为年和月 并通过年月分组是关键
同时注意用月份减去排名值相同的即为连续
