Cleaning Messy Datasets | Dataford Interview Questions

Can you describe a time you had to clean a messy dataset and the specific techniques you used? Using the supplied tables, demonstrate those techniques by producing a cleaned customer record set. Exclude records with missing or invalid emails, retain the latest record for each normalized email, and preserve records without a matching account.

Output

One row per retained customer record with account_id, cleaned_name, cleaned_email, cleaned_phone, and account_status.
Missing phone values remain NULL; unmatched accounts have a NULL status.
Order by cleaned_email ascending.

Schema

raw_customer_records

Column	Type	Description
record_idPK	INT	Unique identifier for the raw record
account_id	INT	Referenced customer account identifier
full_name	VARCHAR(150)	Customer name as captured from the source
email	VARCHAR(255)	Customer email as captured from the source
phone	VARCHAR(50)	Customer phone number with inconsistent formatting
captured_at	TIMESTAMP	Timestamp when the source record was captured

customer_accounts

Column	Type	Description
account_idPK	INT	Unique customer account identifier
account_status	VARCHAR(20)	Current account status
segment	VARCHAR(30)	Customer account segment

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Problem