“Application Instantiation Error: No database selected” Joomla Error

A new client emailed us that he was seeing the following error on his Joomla website:

Error displaying the error page

He told us that he started seeing the above error when the hosting company moved his website from one server to another. He told us that the hosting company debugged the issue for a long time, but couldn’t determine the problem.

So, we logged in to the cPanel account of the website, and then we went to the File Manager, and from there, we edited the configuration.php file and changed the value of $error_reporting from default to maximum (we couldn’t do that through the backend of the Joomla website since both the backend and the frontend were showing the same error).

When we visited the website again, it displayed the following error:

Error displaying the error page: Application Instantiation Error: No database selected

Aha, now we have a real, meaningful error, and we know that it has to do with the database. But, are the connection parameters incorrect? No, because if they were, then we would see the following error:

Error displaying the error page: Application Instantiation Error: Could not connect to MySQL.

So, we know for sure that the database host, username, and password (these are all set in the configuration.php file) are all correct. But, is the database name correct? So, we checked the name of the database in the configuration.php and we matched it to the one in phpMyAdmin and it did.

We were confused – we were confident that the database parameters were correct, yet we were sure that the problem was with the database parameters (yes, we know, it doesn’t make any sense!). So, we went back to the cPanel homepage, we clicked on the MySQL databases icon, we created another database user, and we assigned that user to the database (we granted the user all the privileges). We then modified the configuration.php values for $user and $password to match those of the user that we just created. We loaded the website and this time it worked. But why wasn’t it working for the old user?

We investigated the issue by comparing the user that we have created and the previous user, and it didn’t take us long to see the different: the old user didn’t have any privileges on the database. It seems that the user was created by the hosting company, but it was not assigned any privileges to the database. So, under the Add User To Database section on the MySQL Databases page in cPanel, we selected the old user under User, and then we selected the Joomla database under Database, we then clicked on the Add button, and on the next page, we clicked on the checkbox ALL PRIVILEGES to select all possible database privileges, and finally we clicked on Make Changes at the bottom. We reverted back the configuration.php to what it was and, unsurprisingly, the website worked!

So, if you have the same problem on your website, then make sure that the right privileges are assigned to the database user on the Joomla database. If you have already done that and it didn’t fix the problem, or if you need help doing that, then please contact us. Our fees are right, our work is clean, and our Joomla experience is unquestionable!

One Response to ““Application Instantiation Error: No database selected” Joomla Error”
  1. Comment by Thomas Wollenweber — January 4, 2022 @ 10:46 am

    Thank you so much for publishing this information. I also spent several hours trying to find a solution to the very same issue. Until I found your advice. THANK YOU AGAIN.

    Best wishes for the New Year
    and greetings from Germany

    Thomas Wollenweber

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