SQL Running Total with CTEs | Dataford Interview Questions

Write a SQL query using window functions and Common Table Expressions (CTEs) to find the running total of client transactions.

Use the provided clients and transactions tables. Include only transactions associated with a known client, treat a NULL amount as zero for accumulation, and use transaction ID to break date ties.

Output

One row per valid transaction with transaction_id, client_id, client_name, transaction_date, amount, and running_total.
Include transactions in chronological order within each client, sorted by client name and transaction ID for ties.

Schema

clients

Column	Type	Description
client_idPK	INT	Unique client identifier
client_name	VARCHAR(100)	Client display name
client_segment	VARCHAR(30)	Optional client segment

transactions

Column	Type	Description
transaction_idPK	INT	Unique transaction identifier
client_id	INT	Client associated with the transaction
transaction_date	DATE	Date of the transaction
amount	NUMERIC(12,2)	Transaction amount

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