SELECT DAY(sale_date) AS day, SUM(amount) FROM sales GROUP BY DAY(sale_date); 
-- Output:
day    sum_amount
---    ----------
1      45678.90
2      34567.89
3      56789.12
4      43210.98
5      54321.87
6      65432.10
7      76543.21
8      45678.90
9      34567.89
...    ...
30     56789.12
31     45678.90

SELECT * FROM transactions WHERE DAY(transaction_date) = DAY(LAST_DAY(transaction_date)); 
-- Output:
transaction_id    transaction_date    amount    status
--------------    ----------------    ------    -------
T145             2024-01-31          567.89    Complete
T167             2024-02-29          789.12    Complete
T189             2024-03-31          456.78    Pending
T234             2024-04-30          678.90    Complete
T256             2024-05-31          890.12    Processing

SELECT DAY(event_date) AS day_of_month, COUNT(*) AS events FROM events GROUP BY DAY(event_date);
-- Output:
day_of_month    events
------------    ------
1               45
2               38
3               42
4               39
5               41
...             ...
30              37
31              40