Average Department vs Enterprise SQL | Dataford Interview Questions

Tavant leadership wants a salary comparison view for workforce planning across its engineering and delivery teams. Write a PostgreSQL query that shows each department's average salary alongside the average salary across the entire enterprise.

Requirements

Return every department, including departments with no assigned employees.
Calculate the average non-null salary for each department.
Calculate the overall average non-null employee salary once and display it beside every department.
Round both averages to two decimal places and order the results by department ID.

Schema

departments

Column	Type	Description
department_idPK	INT	Unique department identifier
department_name	VARCHAR(100)	Department name

employees

Column	Type	Description
employee_idPK	INT	Unique employee identifier
employee_name	VARCHAR(100)	Employee name
department_id	INT	Employee department identifier
salary	NUMERIC(10,2)	Annual employee salary

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