Problem
In a company's org chart, top-level executives and founders typically have no manager — their manager_id is NULL because no one is above them in the hierarchy. When HR builds an organizational tree or audits reporting relationships, they start by identifying these root nodes. Using the employees table, return id and name for every employee whose manager_id is NULL, ordered by name.
Schema
employees
| column | type |
|---|
| id | INTEGER |
| name | TEXT |
| department | TEXT |
| salary | INTEGER |
| manager_id | INTEGER (NULL if no manager) |
Sample Data
| id | name | department | salary | manager_id |
|---|
| 1 | Alice | Engineering | 150000 | NULL |
| 2 | Bob | Engineering | 100000 | 1 |
| 3 | Carol | HR | 120000 | NULL |
| 4 | Dave | Marketing | 90000 | 3 |
Expected Output