ALTER TABLE `cities` ADD COLUMN `slug` VARCHAR(255) NOT NULL AFTER `name`;
UPDATE `cities` SET `slug` = 'krakow' WHERE `name` = 'Kraków';
UPDATE `cities` SET `slug` = 'warszawa' WHERE `name` = 'Warszawa';
UPDATE `cities` SET `slug` = 'wroclaw' WHERE `name` = 'Wrocław';
UPDATE `cities` SET `slug` = 'poznan' WHERE `name` = 'Poznań';
UPDATE `cities` SET `slug` = 'gdansk' WHERE `name` = 'Gdańsk';
UPDATE `cities` SET `slug` = 'szczecin' WHERE `name` = 'Szczecin';
UPDATE `cities` SET `slug` = 'lodz' WHERE `name` = 'Łódź';
UPDATE `cities` SET `slug` = 'lublin' WHERE `name` = 'Lublin';
UPDATE `cities` SET `slug` = 'katowice' WHERE `name` = 'Katowice';