Running Total with Window | Dataford Interview Questions

How can you create a window function in PySpark to calculate a running total?

Asked in the technical interview stage. For this SQL exercise, write the PostgreSQL equivalent using the provided transaction data.

Output

Return one row per transaction with account_id, transaction_date, transaction_id, amount, and running_total.
Calculate the cumulative amount separately for each account, treating a missing amount as zero.
Order by account_id, transaction_date, and transaction_id.

account_transactions

Column	Type	Description
transaction_idPK	INT	Unique transaction identifier
account_id	VARCHAR(20)	Account associated with the transaction
transaction_date	DATE	Date on which the transaction occurred
amount	DECIMAL(12,2)	Transaction amount, which may be missing

Your question is Running Total with Window. Start with the requirements and the one table in the Question tab.

Run and submit as often as you like. When you're ready, talk me through your approach or go straight to the code.

How can you create a window function in PySpark to calculate a running total?

Asked in the technical interview stage. For this SQL exercise, write the PostgreSQL equivalent using the provided transaction data.

Return one row per transaction with account_id, transaction_date, transaction_id, amount, and running_total.
Calculate the cumulative amount separately for each account, treating a missing amount as zero.
Order by account_id, transaction_date, and transaction_id.

account_transactions

Column	Type	Description
transaction_idPK	INT	Unique transaction identifier
account_id	VARCHAR(20)	Account associated with the transaction
transaction_date	DATE	Date on which the transaction occurred
amount	DECIMAL(12,2)	Transaction amount, which may be missing

Your question is Running Total with Window. Start with the requirements and the one table in the Question tab.

Run and submit as often as you like. When you're ready, talk me through your approach or go straight to the code.