-- Müşteriler tablosuna il, ilçe ve referans alanları ekler
ALTER TABLE `musteriler`
  ADD `il_id` int(11) unsigned NULL AFTER `adres`,
  ADD `ilce_id` int(11) unsigned NULL AFTER `il_id`,
  ADD `referans_kaynagi` varchar(50) NULL AFTER `ilce_id`,
  ADD CONSTRAINT `fk_musteriler_il` FOREIGN KEY (`il_id`) REFERENCES `iller` (`id`) ON DELETE SET NULL ON UPDATE CASCADE,
  ADD CONSTRAINT `fk_musteriler_ilce` FOREIGN KEY (`ilce_id`) REFERENCES `ilceler` (`id`) ON DELETE SET NULL ON UPDATE CASCADE;