Can’t select database

I cant create a new wordpress site. i am getting this message:

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We were able to connect to the database server (which means your username and password is okay) but not able to select the alex database.

Are you sure it exists?
Does the user have permission to use the alex database?
On some systems the name of your database is prefixed with your username, so it would be like username_alex. Could that be the problem?

If you don’t know how to set up a database you should contact your host. If all else fails you may find help at the WordPress Support Forums.
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i am absolutely possitive i have a database with the name alex, as it says, if i could i would gladly email any one with the screen shot of the database.

I am running a mamp server on a MAC OS.

There is one more thing, i was using xampp a few days ago and i changed the password for the localserver after that i wasnt able to view any of my databases. For that reason i deleted xampp and installed mamp, after that i was able to at least create a new database which means that the problem should be resolved seeing that when mamp is installed it resets password and user name to blank.

I have really tried everything, any suggestions would be greatly appreciated