Third Largest SQL Query | Dataford Interview Questions

Airtel Digital uses Airtel Thanks transaction data to analyze successful mobile data-pack purchases. Write a PostgreSQL query to find the third-largest distinct purchase amount and return every matching transaction with the associated customer name.

Requirements

Consider only transactions where product_type = 'DATA' and status = 'SUCCESS'.
Exclude NULL amounts and transactions whose customer does not exist in customers.
Rank distinct amounts from highest to lowest using a window function, then return all transactions at rank 3.
Order the output by amount descending and transaction ID ascending.

Schema

customers

Column	Type	Description
customer_idPK	INTEGER	Unique customer identifier
customer_name	VARCHAR(100)	Customer's full name
city	VARCHAR(50)	Customer's registered city

transactions

Column	Type	Description
transaction_idPK	INTEGER	Unique transaction identifier
customer_id	INTEGER	References customers.customer_id
product_type	VARCHAR(20)	Type of Airtel product purchased
status	VARCHAR(20)	Transaction processing status
amount	NUMERIC(10,2)	Purchase amount in Indian rupees

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