Accounts That Went Negative

Return accounts whose running balance fell below zero at any point, with the lowest balance reached. Order by account.

Table schema

Transactions(id INT PRIMARY KEY, account VARCHAR(5), amount INT)

Sample data

id | account | amount
1 | A | 100
2 | A | -30
3 | B | 50
4 | A | -90
5 | B | -20