DO $$
BEGIN
  IF EXISTS (
    SELECT 1
    FROM information_schema.table_constraints
    WHERE table_name = 'prestataires'
      AND constraint_name = 'fk_prestataires_vitrine'
  ) THEN
    ALTER TABLE prestataires DROP CONSTRAINT fk_prestataires_vitrine;
  END IF;
END $$;

ALTER TABLE prestataires
  DROP COLUMN IF EXISTS vitrine_id;