How to change database connection from a local storage to a web based one

I have developed my database driven side on my local computer with a copy of the original web based MYSQL Database. I use as target a local folder. The definition is in the Project as localhost. It works.
Second
I also created a database connection to the local copy of the MYSQL Database.and it works.

Now to my Problem.

I want to publish the side in the www and want to connect to the original side on the providers server.

I change the target to my website in www. for uploading al files. It works!
I also change the database connection to the MYSQL on the providers server. It works as well (no connection error)

I change the target from local to web (and save it)
I change the database connection to the web side one.

But when I enter the www page no datas are shown.

What have I overseen?