SQL with and without Window Functions | Dataford Interview Questions

2 SQL questions like multiple employes sales in each month and how to do with and with out window functions

Asked in the technical_round_2 stage. Reported follow-up: write the same logic in PySpark using data loaded from a CSV or text file in an S3 location.

Write a PostgreSQL query for completed sales from January through March 2025. Return monthly sales per employee and their rank within that month. Also explain how to produce the same result without window functions.

Output

One row per employee with completed sales in each month.
Columns: employee_id, employee_name, sales_month, monthly_sales, and monthly_rank.
Order by month, rank ascending, and employee ID ascending. Ties share the same rank.

Schema

employees

Column	Type	Description
employee_idPK	INT	Unique employee identifier
employee_name	VARCHAR(100)	Employee full name

sales

Column	Type	Description
sale_idPK	INT	Unique sale identifier
employee_id	INT	Employee associated with the sale
sale_date	DATE	Date when the sale occurred
amount	NUMERIC(10,2)	Sale amount
status	VARCHAR(20)	Sale processing status

Your question is SQL with and without Window Functions. Start with the requirements and the two tables in the Question tab.

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Problem