Customer Transactions SQL Query | Dataford Interview Questions

Continental Finance wants to identify customers showing concentrated monthly transaction activity. Write a PostgreSQL query that reports customers with more than three completed transactions in a calendar month, using only transactions linked to active accounts.

Requirements

Join customers, accounts, and transactions.
Include only transactions from active accounts with completed status.
Group transactions by customer and calendar month using PostgreSQL date functions.
Return the customer, month, transaction count, and total amount. Treat a NULL amount as zero.
Keep only groups with more than three transactions and order by total amount descending.

Schema

customers

Column	Type	Description
customer_idPK	INT	Unique customer identifier
customer_name	VARCHAR(100)	Customer full name

accounts

Column	Type	Description
account_idPK	INT	Unique account identifier
customer_id	INT	Customer who owns the account
account_status	VARCHAR(20)	Current account status

transactions

Column	Type	Description
transaction_idPK	INT	Unique transaction identifier
account_id	INT	Account associated with the transaction
transaction_date	DATE	Date the transaction occurred
status	VARCHAR(20)	Transaction processing status
amount	NUMERIC(12,2)	Transaction amount, which may be NULL

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