How to Parse a Domain Name from a URL using SQL

Sometimes you may need to parse a domain name from a string expression which identifies a URL of a web address.
I tried to create a user-defined function which parses the url string for the domain name.
On SQL Server you can use this function by running the Create Function script below and try how the function works on different situations by running the sample select query to see the results.
I used a variable type nvarchar for keeping the url address since localized address names will probably be used on some places with an increasing atitude.
The first step in the user defined function is defining the url address string is in HTTP protocol or HTTPS protocol.
Then the sql statements controls the url address variable for "/", and "." characters and parses the url address string to fetch the domain name.

CREATE FUNCTION Parse_For_Domain_Name (
@url nvarchar(255)
)
returns nvarchar(255)

AS

BEGIN

declare @domain nvarchar(255)

-- Check if there is the "http://" in the @url
declare @http nvarchar(10)
declare @https nvarchar(10)
declare @protocol nvarchar(10)
set @http = 'http://'
set @https = 'https://'

declare @isHTTPS bit
set @isHTTPS = 0

select @domain = CharIndex(@http, @url)

if CharIndex(@http, @url) > 1
begin
if CharIndex(@https, @url) = 1
set @isHTTPS = 1
else
select @url = @http + @url
-- return 'Error at : ' + @url
-- select @url = substring(@url, CharIndex(@http, @url), len(@url) - CharIndex(@http, @url) + 1)
end

if CharIndex(@http, @url) = 0
if CharIndex(@https, @url) = 1
set @isHTTPS = 1
else
select @url = @http + @url

if @isHTTPS = 1
set @protocol = @https
else
set @protocol = @http

if CharIndex(@protocol, @url) = 1
begin
select @url = substring(@url, len(@protocol) + 1, len(@url)-len(@protocol))
if CharIndex('/', @url) > 0
select @url = substring(@url, 0, CharIndex('/', @url))

declare @i int
set @i = 0
while CharIndex('.', @url) > 0
begin
select @i = CharIndex('.', @url)
select @url = stuff(@url,@i,1,'/')
end
select @url = stuff(@url,@i,1,'.')

set @i = 0
while CharIndex('/', @url) > 0
begin
select @i = CharIndex('/', @url)
select @url = stuff(@url,@i,1,'.')
end

select @domain = substring(@url, @i + 1, len(@url)-@i)
end

return @domain

END
GO
 

Here is the sample select query which you can use to test the user defined function Parse_For_Domain_Name which is created to parse a url address to fetch the domain name.

select
dbo.Parse_For_Domain_Name('https://sql.kodyaz.com/articles/article.aspx?http://www.eralper.com'),
dbo.Parse_For_Domain_Name('http://sql.kodyaz.com/articles/article.aspx?http://www.eralper.com'),
dbo.Parse_For_Domain_Name('http://sql.kodyaz.com/'),
dbo.Parse_For_Domain_Name('http://www.kodyaz.com/'),
dbo.Parse_For_Domain_Name('https://www.kodyaz.com/'),
dbo.Parse_For_Domain_Name('www.kodyaz.com/?http://www.eralper.com'),
dbo.Parse_For_Domain_Name('sql.kodyaz.com'),
dbo.Parse_For_Domain_Name('rs.sql.kodyaz.com'),
dbo.Parse_For_Domain_Name('kodyaz.com'),
dbo.Parse_For_Domain_Name('shttp://kodyaz.com')
go