How do you JOIN two MySQL tables where the data is NOT in the other table?

SELECT PETS.NAME
FROM PETS
   LEFT OUTER JOIN LOST_PETS
     ON PETS.PET_ID = LOST_PETS.PET_ID
WHERE LOST_PETS.PET_ID IS NULL;

SELECT *
FROM pets LEFT OUTER JOIN pets-lost ON pets.id = pets-lost.id
WHERE pets-lost.id IS NULL;