Mapping of zipcode and prefecture/city.

If the information is changed, it must be updated. For Japanese, data is on Japan post page.

Column	Type	Constraint	Description
id	INTEGER	PRIMARY KEY	Identifier.
zipcode	TEXT	NOT NULL	Zipcode.
prefecture	TEXT	NOT NULL	Prefecture.
city	TEXT	NOT NULL	City.
address	TEXT	NOT NULL	Address.

CREATE TABLE zipcode_map(
id          INTEGER  PRIMARY KEY,
zipcode     TEXT     NOT NULL,
prefecture  TEXT     NOT NULL,
city        TEXT     NOT NULL,
address     TEXT     NOT NULL
);