Employees Without a Manager - Easy SQL Filtering Interview Problem

Problem

In any org chart, there is usually only one person at "the top". That person's manager_id is NULL because there's no one above them. 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

id	name
1	Alice
3	Carol

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