How do you update a table using JOIN in SQL Server?

Short answer: T-SQL supports UPDATE ... FROM with JOINs. Be careful with one-to-many joins (nondeterministic updates). Prefer MERGE or ensure uniqueness.

Sample solution

UPDATE e
SET e.DepartmentName = d.Name
FROM Employees e
INNER JOIN Departments d ON d.DepartmentId = e.DepartmentId;

Mention nondeterministic update risk if multiple matched rows exist.