CREATE TABLE ip_addresses (
        id      INTEGER PRIMARY KEY AUTO_INCREMENT,
        string  VARCHAR(15),
        UNIQUE(string)
) Type=InnoDB;

CREATE TABLE devices (
        id      INTEGER PRIMARY KEY AUTO_INCREMENT,
        name    VARCHAR(255),
        mac_address VARCHAR(17),
        ip_static_id    INTEGER,

        FOREIGN KEY (ip_static_id)
                REFERENCES ip_addresses(id),
        INDEX(ip_static_id),
        UNIQUE(mac_address)
) Type=InnoDB;

CREATE TABLE activity (
        id      INTEGER PRIMARY KEY AUTO_INCREMENT,
        minute  DATETIME,
        counter BIGINT,
        device_id       INTEGER NOT NULL,
        ip_address_id   INTEGER NOT NULL,

        FOREIGN KEY (device_id)
                REFERENCES devices(id),
        FOREIGN KEY (ip_address_id)
                REFERENCES ip_addresses(id),
        INDEX(device_id),
        INDEX(ip_address_id)
) Type=InnoDB;