IP to Country with SQL Server

I have recently yet again come across a need to get country information from IP addresses out of SQL server. I use the GeoIP Country data that is freely available from MaxMind.

The GeoIP data is made available in CSV format with the following fields:

Column	Type	Description
1 (FirstIP)	varchar(15)	First IP address (dotted)
2 (LastIP)	varchar(15)	Last IP address (dotted)
3 (FirstNum)	unsigned int	First IP address (long)
4 (LastNum)	unsigned int	Last IP address (long)
5 (CountryCode)	char(2)	Country code
6 (CountryName)	varchar(50)	Country name

As you can see, the IP address ranges are available in dotted or integral (long) formats. Unfortunately, SQL server doesn’t allow us to create unsigned columns, so we need to convert either from unsigned to signed, or from dotted to long. Since we will presumably need to convert dotted to long in the future, we may as well go that route. For now, just create tables like so:

Countries
Column	Type	Comments
CountryCode	char(2) not null	Primary Key
CountryName	varchar(50) not null

GeoIP
Column	Type	Comments
FirstNum	int not null
LastNum	int not null
CountryCode	char(2) not null	Foreign key: Countries.CountryCode

Import the CSV data into a temporary table, which I assume you’ll call GeoIP_temp. You can then fill your Countries table like so:

INSERT INTO Countries (CountryCode, CountryName)
SELECT DISTINCT CountryCode, CountryName
FROM GeoIP_temp

Now let’s look at getting the IP addresses into the system in a format that we can use, by converting the dotted addresses to longs. To do this, we’ll make a User-Defined Function (UDF) in SQL server. The original version of this code doesn’t actually work, so I’ve modified it a bit.

CREATE FUNCTION dbo.NumFromIP (
    @ip VARCHAR(15)
) RETURNS INT
AS
BEGIN
    DECLARE @rv BIGINT,
        @o1 BIGINT,
        @o2 BIGINT,
        @o3 BIGINT,
        @o4 BIGINT
    SELECT
        @o1 = CONVERT(BIGINT, PARSENAME(@ip, 4)),
        @o2 = CONVERT(BIGINT, PARSENAME(@ip, 3)),
        @o3 = CONVERT(BIGINT, PARSENAME(@ip, 2)),
        @o4 = CONVERT(BIGINT, PARSENAME(@ip, 1))
    IF (@o1 BETWEEN 0 AND 255)
        AND (@o2 BETWEEN 0 AND 255)
        AND (@o3 BETWEEN 0 AND 255)
        AND (@o4 BETWEEN 0 AND 255)
    BEGIN
        SET @rv = (@o1 * 16777216) +
            (@o2 * 65536) +
            (@o3 * 256) +
            (@o4)
        IF (@rv > 2147483647)
        BEGIN
            SET @rv = @rv - 4294967296
        END
    END
    ELSE
        SET @rv = -1
    RETURN CONVERT(INT,@rv)
END

That last IF statement is what does the conversion from unsigned to signed and allows us to use a regular int instead of a bigint.

The inverse of this function, to convert back from long to dotted, is here:

CREATE FUNCTION dbo.IPFromNum (
    @ip INT
) RETURNS VARCHAR(15)
AS
BEGIN
    DECLARE @o1 INT,
        @o2 INT,
        @o3 INT,
        @o4 INT,
        @bip BIGINT
    SET @bip = @ip
    IF @bip < 0
        SET @bip = @bip + 4294967296
    IF @bip > 4294967295
        RETURN '255.255.255.255'
    IF @bip < 0
        RETURN '0.0.0.0'
    SET @o1 = @bip / 16777216
    SET @bip = @bip % 16777216
    SET @o2 = @bip / 65536
    SET @bip = @bip % 65536
    SET @o3 = @bip / 256
    SET @bip = @bip % 256
    SET @o4 = @bip
    RETURN
        CONVERT(VARCHAR(4), @o1) + '.' +
        CONVERT(VARCHAR(4), @o2) + '.' +
        CONVERT(VARCHAR(4), @o3) + '.' +
        CONVERT(VARCHAR(4), @o4)
END

You will then need to transfer the data into your GeoIP table, like so:

INSERT INTO GeoIP (FirstNum, LastNum, CountryCode)
SELECT dbo.NumFromIP(FirstIP), dbo.NumFromIP(LastIP), CountryCode
FROM GeoIP_temp

You now have everything you need to do basic GeoIP lookup, like so:

SELECT c.CountryName, COUNT(*) AS HowMany
FROM Countries AS c
    INNER JOIN GeoIP AS g ON (c.CountryCode = g.CountryCode)
    INNER JOIN Logs AS l ON (dbo.NumFromIP(ip) BETWEEN g.FirstNum AND g.LastNum)
GROUP BY c.CountryName
ORDER BY 2 DESC

However, this query can be a rather lengthy process, as BETWEEN operations are basically unindexable table scans and take quite some time to run. Instead, you may want to modify your table to automagically lookup and store the country information as the IP address is inserted or updated. This little bit of denormalization is handled perfectly with a small trigger:

CREATE TRIGGER [ip_fix] ON dbo.Logs
AFTER INSERT, UPDATE
AS
SET NOCOUNT ON
IF UPDATE(ip) BEGIN
    UPDATE Logs SET
        CountryCode = (
            SELECT CountryCode
            FROM GeoIP
            WHERE dbo.NumFromIP(Logs.ip) BETWEEN FirstNum AND LastNum
        )
    WHERE (id IN (SELECT id FROM inserted))
END
SET NOCOUNT OFF

This presumes, of course, that your Logs table has a primary key called id and that you’ve added in the CountryCode field. This trigger will slow down inserts and updates slightly, so you may instead choose to update the country codes asynchronously (nightly, hourly, whatever) if you care more about update speed than query speed. And don’t forget to index your CountryCode field in any tables you add it to!