Joining Profiles With Transactions | Dataford Interview Questions

Perform a multi-table JOIN to combine user profile data with monthly transaction logs at Credit Karma, ensuring you account for users with no transaction history.

Use the January through March 2025 reporting period. Return one row for every user and reporting month, including users and months with no matching transactions.

Output

Return user_id, full_name, state, membership_tier, month_start, transaction_count, and monthly_transaction_amount.
Use zero for missing transaction counts and amounts.
Order by user_id, then month_start ascending.

Schema

user_profiles

Column	Type	Description
user_idPK	INT	Unique Credit Karma user identifier
full_name	VARCHAR(100)	User's full name
state	VARCHAR(2)	Two-letter US state code
membership_tier	VARCHAR(20)	Credit Karma membership tier
credit_score	INT	User's current credit score

monthly_transaction_logs

Column	Type	Description
log_idPK	INT	Unique transaction-log identifier
user_id	INT	User associated with the transaction log
transaction_month	DATE	First day of the transaction month
amount	DECIMAL(12,2)	Transaction amount recorded in the log

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