Show all departments even if no employees (outer join)?

Short answer: Show all departments even if no employees (outer join) var allDepts = from d in departments join e in employees on d.Name equals e.Department into empGroup from eg in empGroup.DefaultIfEmpty() select new { Dept = d.Name, EmpName = eg?.Name ?? "No Employee"

Real-world example (ShopNest)

A sales report joins orders and customers, then GroupBy(c => c.City) to show revenue per city.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.