Cleaning a Messy Dataset | Dataford Interview Questions

How would you approach cleaning a messy dataset?

For this SQL exercise, treat a row as clean when its required fields are present, its event name is not blank, and its revenue is nonnegative. Write a query that returns only clean records and removes surrounding whitespace from event names.

Output

One row per clean event with columns event_id, player_id, event_name, event_date, and revenue_usd
Exclude rows with missing required values, blank event names, or negative revenue
Order by event_date ascending, then event_id ascending

Schema

game_events

Column	Type	Description
event_idPK	INT	Unique identifier for the raw event record
player_id	INT	Identifier of the player associated with the event
event_name	VARCHAR(100)	Name of the recorded game event
event_date	DATE	Date on which the event occurred
revenue_usd	NUMERIC(10,2)	Revenue associated with the event in US dollars

Your question is Cleaning a Messy Dataset. 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.

Problem

How would you approach cleaning a messy dataset?

Output

One row per clean event with columns event_id, player_id, event_name, event_date, and revenue_usd
Exclude rows with missing required values, blank event names, or negative revenue
Order by event_date ascending, then event_id ascending

Schema

game_events

Column	Type	Description
event_idPK	INT	Unique identifier for the raw event record
player_id	INT	Identifier of the player associated with the event
event_name	VARCHAR(100)	Name of the recorded game event
event_date	DATE	Date on which the event occurred
revenue_usd	NUMERIC(10,2)	Revenue associated with the event in US dollars

Your question is Cleaning a Messy Dataset. 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.