text: CREATE TABLE IF NOT EXISTS Exams (
      id             SERIAL          NOT NULL PRIMARY KEY,
      title          VARCHAR(256)    NOT NULL,
      description    VARCHAR(1024)   NOT NULL DEFAULT '',
      point          INTEGER         NOT NULL,
      created        TIMESTAMP       NOT NULL DEFAULT CURRENT_TIMESTAMP,
      modified       TIMESTAMP       NOT NULL DEFAULT CURRENT_TIMESTAMP,
      from_professor INTEGER         DEFAULT NULL,
  
      FOREIGN KEY (from_professor) REFERENCES Users(id)
  );
  --!!
  DROP TRIGGER IF EXISTS update_exams_modified ON Exams;
  --!!
  CREATE TRIGGER update_exams_modified BEFORE UPDATE
      ON Exams FOR EACH ROW EXECUTE PROCEDURE 
      update_modified_column();
  