Error Establishing Database Connection

First go to cPanel > MySQL and collect this information:

DB1 name:
DB1 user:
DB1 password: (change it if you cannot read it)

DB2 name:
DB2 user:
DB2 password: (change it if you cannot read it)

Next go to cPanel phpMyAdmin and get this information:

DB1 table_prefix:
DB2 table_prefix:
note: At my own host, I have an extra SQL user assigned to both databases so I can use those credentials to see both databases at once at phpMyAdmin.

After gathering the above info, open your two wp-config.php files side-by-side and make certain each has what it should from the above.

If you might be uncertain about each or either site’s URL in the database, edit this and temporarily add it at the top of the respective wp-config.php file/s:

Select and edit one pair of lines or the other — no trailing slashes — then temporarily place a slash after /*toggle on/off* just above them to un-comment them and make them active.

/*-either-*/
/* tell database to recognize and use http://domain.com
/** @ near top of wp-config.php /*toggle on/off*
define('WP_HOME','http://domain.com');
define('WP_SITEURL','http://domain.com');
/*-or-*/
/* tell database to recognize and use http://www.domain.com
/** @ near top of wp-config.php /*toggle on/off*
define('WP_HOME','http://www.domain.com');
define('WP_SITEURL','http://www.domain.com');
/*-end-*/

If you use the above and still have URL trouble, maybe try this in your active theme’s functions.php:

Select and edit one pair of lines or the other — no trailing slashes — then temporarily place a slash after /*toggle on/off* just above them to un-comment them and make them active.

/*-either-*/
/* tell database to recognize and use http://domain.com
/** @ near top of theme functions.php /*toggle on/off*
update_option('siteurl','http://domain.com');
update_option('home','http://domain.com');
/*-or-*/
/* tell database to recognize and use http://www.domain.com
/** @ near top of theme/functions.php /*toggle on/off*
update_option('siteurl','http://www.domain.com');
update_option('home','http://www.domain.com');
/*-end-*/

my database contains about 19 tables labelled things like Ucomments, Uoptions, Ulinks etc

The table prefix is the part immediately preceding _Ucomments, _Uoptions, _Ulinks, _etc. The WordPress default would look something like this:

wp_Ucomments
wp_Uoptions
wp_Ulinks
wp_etc

So, you either have two sets of tables (two “databases”) in one server database (and there is nothing wrong with that as long as each site has its own SQL user) or else you have two databases at the server and with each database having a prefix that might or might not be the same as the other.

database name + table_prefix + table name =
DB1name_prefix1_tables
DB2name_prefix2_tables

Then as entered in wp-config.php (minus table names):

define('DB_NAME', 'database_name_here');

define('DB_USER', 'username_here');

define('DB_PASSWORD', 'password_here');

$table_prefix  = 'wp_';

My original database was labelled db589834258 under this database I had tables all starting with ZctfvVr and then followed by Ucomments etc. So I assume from your comment that the ZctfvVr bit is the table prefix.

Yes, but I have no idea how the ‘U’ came to be at the beginning of ‘comments’…and please forgive me for not questioning that earlier since that is not how WordPress typically does things.

my second database…has some tables labelled wNvQHsBcomments, Boptions etc. plus it has a list of tables labelled ZctfvVrUcomments etc.

Do you have any idea at all about how those table names came to be anything other than ‘_comments’, ‘_options’. _etc? It sounds to me like either you or someone had done some editing outside of phpMyAdmin or else whatever you had used for export/download/upload/import has grossly corrupted things.

I suppose my question now is, should I have both sets of tables present? Do I need to delete some or am I creating a future problem?

You can have more than one set of tables (tables for more than one site) in the same database container (database name) at the server, but I do not do that without first having a specific need or reason such as sharing users.

…the password is no longer encrypted in the wp-config.

It never was, but it might have appeared to be. Passwords are only encrypted inside the actual database where site user credentials are stored.

Also the password I set on the database does not seem to reflect the password set on the wp-login panel that I access via the website. So it seems there are multiple passwords in use which is all very confusing.

Yes, there are different passwords for different things, and they need to be that way as part of overall security:

Server login at host: hosting username
Server login at host: hosting password
note: Some hosts have multiple passwords for doing different things at the server.

SQL user at server: SQL username (unique for each site)
SQL user at server: SQL password

WordPress LogIn: username
WordPress LogIn: password

Recently 1and1 changed their databases from 5.1 to 5.5 and it has intermittent issues that say there’s an error establishing a connection with the database. Look to see if your database is 5.5. It will say it next to it on the My SQL Databases area of your account.