42-01831-maximum-transaction-each-day.sql

-- using subquery

select transaction_id
from Transactions
where (day, amount) in (select date(day), max(amount)
                      from Transactions
                      group by 1)
order by 1

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-- using window function

with CTE as
    (select transaction_id, dense_rank() over(partition by date(day) order by amount desc) as rnk
    from Transactions)

select transaction_id
from CTE
where rnk = 1
order by 1


-- no companies listed