moving or replacing databases for WordPress blogs

hi there,
i have a question about replacing databases on wordpress blogs or even attaching a new database to a wordpress blog.

I really want to see how flexible it is to move databases around and replace them. More of an exercise really if it is possible to do it.

I have two self hosted wordpress blogs in separate folders (blog folder and dev folder) in my public_html folder.

my main blog is
https://www.eddycrosby.com/blog/

my development blog is in a sub domain (resides in public_html/dev)
https://dev.eddycrosby.com/

I want all my posts in my main blog to appear in my development blog.
————————————————————-
so far i have done the following.
I have backed up both databases via C-panel.

I have then gone into MySQLadmin, selected the dev database, dropped the tables and then imported the database from my main blog. that went fine.
But when i go to the development blog’s url i get a blank screen. no error message.

I have tried going into dev blog’s wp-config.php and changing these lines

————————————————————-
// ** MySQL settings – You can get this info from your web host ** //
/** The name of the database for WordPress */
define(‘DB_NAME’, ‘myname_mainblog’);

/** MySQL database username */
define(‘DB_USER’, ‘myname_mainblog);

/** MySQL database password */
define(‘DB_PASSWORD’, ‘xxxx’);
————————————————————-

still get the blank screen.

Do i need to change some other settings?
any help is really appreciated.

thank you