text: CREATE TABLE Teachers (
  	TeacherID INT NOT NULL IDENTITY(101, 1),
  	[Name] VARCHAR(20) NOT NULL,
  	ManagerID INT
  )
  
  INSERT INTO Teachers ([Name], ManagerID)
  VALUES ('John', NULL),
         ('Maya', 106),
         ('Silvia', 106),
         ('Ted', 105),
         ('Mark', 101),
         ('Greta', 101)
  
  ALTER TABLE Teachers
  ADD CONSTRAINT PK_Teachers
  PRIMARY KEY (TeacherID)
  
  ALTER TABLE Teachers
  ADD CONSTRAINT FK_Teachers_ManagerID
  FOREIGN KEY (ManagerID)
  REFERENCES Teachers(TeacherID)