Has the postcard a picture on it?
Does the postcard have a picture on it?
Have(has)在表示"所有"时,变为否定句时,可直接在Have(has)后加not,变为疑问句时可直接把Have(has)放在句首. 当Have(has)不表示"所有"意思时,只能加助动词do(does)来改成否定句和疑问句.
例：
Has he two books?
Does he have two books?