Number of employees under top level manager

 CREATE TABLE employees (

  id INTEGER PRIMARY KEY,

  name VARCHAR(255) NOT NULL,

  managerId INTEGER,

  FOREIGN KEY (managerId) REFERENCES employees(id)

);


INSERT INTO employees(id, name, managerId) VALUES(1, 'Rob', null);

INSERT INTO employees(id, name, managerId) VALUES(2, 'Tom', null);

INSERT INTO employees(id, name, managerId) VALUES(3, 'Roger', 1);

INSERT INTO employees(id, name, managerId) VALUES(4, 'Victor', 3);

INSERT INTO employees(id, name, managerId) VALUES(5, 'John', 4);

INSERT INTO employees(id, name, managerId) VALUES(6, 'Shawn', 2);

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