Can’t select database

Something wrong in your wp-config file.
Check all 4 pieces of info you put in there.

Hi,moshu,I happened have a problem the same as miker’s.I have created a database named “wordpress” by my host’s authorization.Why the hell my wordpress can’t select it??

There might be quite a number of reasons.
For example, on some hosts that use cPanel as your site’s admin tool, will prepend the DB name with your site admin username. Say, if your username to the site was “backpacker” then the DB name would be “backpacker_wordpress”.
But this is just an example, I have no idea how your host server is set up.

Thank you very much.I tryed on using my host’s root name and it didn’t work.I will try on my admin username.

I am getting more and more confused by what you say.
What kind of admin interface do you have? There are instructions for several of them here:
https://www.tamba2.org.uk/wordpress/ – see under Installation.

The error message indicates there is something wrong with the database name.