sql doubt

Question

An employee is a manager if any other employee has their managerId set to the first employees id. An employee who is a manager may or may not also have a manager.

TABLE employees
id INTEGER NOT NULL PRIMARY KEY
managerId INTEGER REFERENCES employees(id)
name VARCHAR(30) NOT NULL
Write a query that selects the names of employees who are not managers.

CREATE TABLE employees (
id INTEGER NOT NULL PRIMARY KEY,
managerId INTEGER REFERENCES employees(id),
name VARCHAR(30) NOT NULL
);

INSERT INTO employees(id, managerId, name) VALUES(1, NULL, 'John');
INSERT INTO employees(id, managerId, name) VALUES(2, 1, 'Mike');

-- Expected output (in any order):
-- name
-- ----
-- Mike

-- Explanation:
-- In this example.
-- John is Mike's manager. Mike does not manage anyone.
-- Mike is the only employee who does not manage anyone.

Answer 1

pls see updated question puny

Answer 2

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Answer 3

I just have some silly questions