How to update one table based on another table's values on the fly? I have a table in the name of ips as below:  

CREATE TABLE `ips` (
 `id` int(10) unsigned NOT NULL DEFAULT '0',
 `begin_ip_num` int(11) unsigned DEFAULT NULL,
 `end_ip_num` int(11) unsigned DEFAULT NULL,
 `iso` varchar(3) DEFAULT NULL,
 `country` varchar(150) DEFAULT NULL
) ENGINE=InnoDB


Lets assume I have a countryid field on this table from country table which is as below:  

CREATE TABLE `country` (
 `countryid` tinyint(3) unsigned NOT NULL AUTO_INCREMENT,
 `name` varchar(50) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL,
 `ordering` smallint(5) unsigned NOT NULL DEFAULT '0',
 `iso` char(2) NOT NULL,
 PRIMARY KEY (`countryid`)
) ENGINE=InnoDB


There is about 100,000 records in ips table. Is there any query for the following scenario:
Check if ips.iso is equal to country.iso, if it's equal then add country.coutryid to that record. I couldn't think of any way to do it. Do you have any idea how to do that?
UPDATE ips INNER JOIN country
    ON ips.iso = country.iso
SET ips.countryid = country.countryid


Using MySQL update multiple table syntax:

14.2.11 UPDATE Syntax

Note that you have two different lengths and data types on your iso columns.  There are, in fact, two separate sets of ISO codes, 2-letter and 3-letter, so you may not in reality be able to join these columns:

ISO 3166-1

The join condition USING (iso) instead of ON ips.iso = country.iso works too.