A simple way to identify websites with the SQL Injection vulnerability is to add some characters to the URL, such as quotes, commas, or periods. For example, if the page is in PHP and you have a URL where you pass a parameter for a search, you can try adding one at the end.
Doing injections will basically be using SQL queries as in the case of union and select and also the famous join. It is only a matter of manipulating in the URL of the page, such as entering the following lines until you can find the error shown above and find the name of the table that is prone or vulnerable to access.
If you observe http://testphp.vulnweb.com/listproducts.php?cat=1, where the ‘GET’ parameter cat can be vulnerable ...
