MySQL combina duas colunas e adiciona em uma nova coluna

ALTER TABLE yourtable ADD COLUMN combined VARCHAR(50);

UPDATE yourtable SET combined = CONCAT(zipcode, ' - ', city, ', ', state);

CREATE TRIGGER insert_trigger
BEFORE INSERT ON yourtable
FOR EACH ROW
SET new.combined = CONCAT(new.zipcode, ' - ', new.city, ', ', new.state);

CREATE TRIGGER update_trigger
BEFORE UPDATE ON yourtable
FOR EACH ROW
SET new.combined = CONCAT(new.zipcode, ' - ', new.city, ', ', new.state);