Left join with fallback message?

Short answer: Left join with fallback message var join = from d in departments join e in employees on d.Name equals e.Department into g from emp in g.DefaultIfEmpty() select new { Department = d.Name, Employee = emp?.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.