Data Cleaning and Prep | Dataford Interview Questions

What methods do you use for data cleaning and preparation?

For this SQL exercise, write a query against raw_encounters that returns usable encounter records with cleaned text fields and valid required values.

Output

One row per accepted encounter, with columns encounter_id, patient_name, department, encounter_date, and charge_amount.
Remove records with missing or blank patient names, departments, dates, or charges, and exclude negative charges.
Trim surrounding whitespace from text values. Order by encounter_date ascending, then encounter_id ascending.

Schema

raw_encounters

Column	Type	Description
encounter_idPK	INT	Unique encounter identifier
patient_name	VARCHAR(100)	Patient name as received from the source system
department	VARCHAR(80)	Department associated with the encounter
encounter_date	DATE	Date of the encounter
charge_amount	NUMERIC(10,2)	Recorded charge amount

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Problem