Mysql update all rows based on select from another table - mysql

Question

I have two tabels;
mysql> describe ipinfo.ip_group_country;
+--------------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------------+-------------+------+-----+---------+-------+
| ip_start | bigint(20) | NO | PRI | NULL | |
| ip_cidr | varchar(20) | NO | | NULL | |
| country_code | varchar(2) | NO | MUL | NULL | |
| country_name | varchar(64) | NO | | NULL | |
+--------------+-------------+------+-----+---------+-------+
mysql> describe logs.logs;
+----------------------+------------+------+-----+---------------------+----------------+
| Field | Type | Null | Key | Default | Extra |
+----------------------+------------+------+-----+---------------------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| ts | timestamp | NO | | CURRENT_TIMESTAMP | |
| REMOTE_ADDR | tinytext | NO | | NULL | |
| COUNTRY_CODE | char(2) | NO | | NULL | |
+----------------------+------------+------+-----+---------------------+----------------+
I can select country code using ip address from first table:
mysql> SELECT country_code FROM ipinfo.`ip_group_country` where `ip_start` <= INET_ATON('74.125.45.100') order by ip_start desc limit 1;
+--------------+
| country_code |
+--------------+
| US |
+--------------+
In logs.logs, I have all the REMOTE_ADDR (ip address) set, but all COUNTRY_CODE entries are empty. Now, I want to populate COUNTRY_CODE appropriately using the ipinfo table. How can I do this?
thanks!

Answer 1

Try
UPDATE logs.logs
SET COUNTRY_CODE = (
SELECT country_code
FROM ipinfo.ip_group_country
WHERE ipinfo.ip_start <= INET_ATON(logs.REMOTE_ADDR)
LIMIT 1
)
WHERE COUNTRY_CODE IS NULL
If it fails saying the column types must match, you'll have to alter your logs.logs table so that the REMOTE_ADDR column is the same type (varchar(20)) as the ip_cidr table.

Answer 2

In a single-table update you use update t1 set c1=x where y.
In a multi-table update you use update t1, t2 set t1.c1=t2.c2 where t1.c3=t2.c4
Here's the relevant documentation http://dev.mysql.com/doc/refman/5.0/en/update.html
What you're looking for is something along the lines of (editted) update logs.logs as l, ipinfo.ip_group_country as c set l.COUNTRY_CODE=c.country_code where c.ip_start <= INET_ATON(l.REMOTE_ADDR) order by c.ip_start asc
Edit: you're right, the max() in the original answer I provided could not work. The query above should, although it will likely be less efficient than something like the approach in the answer provided below.