All we needed is a vulnerability webpage. Lets say you have a url like this
http://www.site.com/section.php?id=51
and that it is prone to sql injection because the developer of that site did not properly escape the parameter id.
This can be simply tested by trying to open the url
http://www.site.com/section.php?id=51'
We just added a single quote in the parameter. If this url throws an error then it is clear that the database has reacted with an error because it got an unexpected single quote..
To understand the process please change video quality to 1080p and watch in HD Quality