text: ALTER TABLE vets ADD COLUMN city VARCHAR(100) AFTER last_name;
  
  UPDATE vets SET city=NULL WHERE id = 1;
  UPDATE vets SET city='Canton' WHERE id = 2;
  UPDATE vets SET city='Boston' WHERE id = 3;
  UPDATE vets SET city=NULL WHERE id = 4;
  UPDATE vets SET city='Newton' WHERE id = 5;
  UPDATE vets SET city='Cambridge' WHERE id = 6;
  