Window Functions for Second Highest | Dataford Interview Questions

Write a SQL query using window functions to find the second-highest transaction amount for each customer.

Use the transactions table. Treat the second-highest amount as the second-highest distinct non-null amount. Customers with fewer than two distinct non-null amounts should be excluded.

Output

One row per eligible customer
Columns: customer_id, second_highest_amount
Order by customer_id ascending

Schema

transactions

Column	Type	Description
transaction_idPK	INT	Unique transaction identifier
customer_id	INT	Identifier of the customer who made the transaction
amount	NUMERIC(12,2)	Transaction amount

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