SQL Query: Maximum Transaction Each Day

QUESTION: Table: Transactions

+----------------+----------+
| Column Name    | Type     |
+----------------+----------+
| transaction_id | int      |
| day            | datetime |
| amount         | int      |
+----------------+----------+
transaction_id is the primary key for this table.
Each row contains information about one transaction.


Write an SQL query to report the IDs of the transactions with the maximum amount on their respective day. If in one day there are multiple such transactions, return all of them.

Return the result table in ascending order by transaction_id.

The query result format is in the following example:



Transactions table:
+----------------+--------------------+--------+
| transaction_id | day                | amount |
+----------------+--------------------+--------+
| 8              | 2021-4-3 15:57:28  | 57     |
| 9              | 2021-4-28 08:47:25 | 21     |
| 1              | 2021-4-29 13:28:30 | 58     |
| 5              | 2021-4-28 16:39:59 | 40     |
| 6              | 2021-4-29 23:39:28 | 58     |
+----------------+--------------------+--------+

Result table:
+----------------+
| transaction_id |
+----------------+
| 1              |
| 5              |
| 6              |
| 8              |
+----------------+
"2021-4-3"  --> We have one transaction with ID 8, so we add 8 to the result table.
"2021-4-28" --> We have two transactions with IDs 5 and 9. The transaction with ID 5 has an amount of 40, while the transaction with ID 9 has an amount of 21. We only include the transaction with ID 5 as it has the maximum amount this day.
"2021-4-29" --> We have two transactions with IDs 1 and 6. Both transactions have the same amount of 58, so we include both in the result table.
We order the result table by transaction_id after collecting these IDs.

SOLUTION:

step1) Get each day transaction of max amount
step2) Make a join of transaction table with above cte on date and amount

;with highestAmt as 
(select date(day) as day, max(amount) as amount from Transactions 
group by date(day))
,resultCte as
(select t.transaction_id from Transactions t
inner join highestAmt h 
on date(t.day) = h.day and t.amount = h.amount)
select transaction_id from resultCte
order by transaction_id asc

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