SQL: Duplicate Rows and Top Percent | Dataford Interview Questions

Altimetrik's Workforce Directory team needs a validation query for employee extracts. Using the tables below, write PostgreSQL SQL that produces both a deliberately duplicated employee row and the first 50% of eligible workforce records.

Requirements

Join employees to departments and retain only active employees with a matching department.
Return the row for employee_id = 104 exactly twice using UNION ALL.
Return the first half of eligible employees, ordered by ascending employee_id. Use NTILE(2) so the query remains data-driven.
Add an operation column with duplicated or first_half, and sort the final result by operation and employee ID.

Schema

employees

Column	Type	Description
employee_idPK	INT	Unique employee identifier
employee_name	VARCHAR(100)	Employee full name
department_id	INT	Referenced department identifier
employment_status	VARCHAR(20)	Current employment status
hire_date	DATE	Date the employee joined
email	VARCHAR(150)	Work email address

departments

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

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Problem