You can find which database belongs to each domain as shown below. It is recommended to make a note of each Domain’s database (Domain name + Database name) for future reference.

How to identify each domain’s database

Access your Control Panel, go to phpMyAdmin. You will see a list of databases wrdp1, wrdp2, etc.

Select the first database wrdp1, by clicking on it.

A list of database tables will appear as shown below. Click the first icon that appears next to table wp_options to browse.

The first 2 entries shown in this table are:
siteurl
blogname

You have identified the domain which this database belongs to. Do the same for each database and you will have identified the databases of all your domains.

Reward yourself with a beverage of choice.

Note: This article was written in response to a question in the comment

http://gnetwork.com.au/wordpress/restore-wordpress-database/comment-page-1#comment-3112

on the article Restore WordPress Database

The easy and secure way, using phpMyAdmin. A good backup copy of your database can be Restored simply, even if your current database has been corrupted!

Required for phpMyAdmin Restore of WordPress database

• Hosting Control Panel access, like cPanel or Plesk, including username and password – obtained from hosting admin.
• Backup of WordPress Database Zip file

Always have a Backup!

How to backup? Click the link below

• How to Backup your WordPress Database

Once you have a backup Zip file of your database, and access to your hosting Control Panel – ready to go!

Using phpMyAdmin to Restore WordPress Database

• Go Login to your Control Panel
• Scroll menus for a reference to Databases – Click on phpMyAdmin link

• phpMyAdmin homepage – Top left corner shows Database names, WordPress Database ends in “_wrdp1″ or similar. Click on the database name you would like to Restore to, see picture below. If there is no database intact, Create one, or Install WordPress, then return. Click on the database name you would like to Restore to.

The next screen appears, showing current database with tables revealed.

On the same page, Scroll down
Click Check All to select all tables – these will be trashed, to make way for the backup, which will slide into an empty database!
Select [Drop] to drop all the tables – When prompted, Click YES to complete.

You will now have an empty database called whatever_wrdp1

Click Import on the top menu, to upload your WordPress Database Backup

The Import screen shows next

Click [Browse] button to Select your backup Zip file on your computer.
Click [Go] button to upload – Restore your good database.

You are done. Congratulations, your WordPress Database is Restored!

Additional Information:
Restoring Your Database From Backup – WordPress Codex

The easy and secure way, using phpMyAdmin. Backup of your database should be done regularly, especially before installing a Plugin or Upgrading WordPress. Then, when and if trouble arises, you have an entire copy of your data including users, pages, posts, comments, plugin variables, settings, etc. The only things not backed up are your files on server, photos, modified files, and the like – see below about FTP backup.

Required for phpMyAdmin Backup of WordPress database

• Hosting Control Panel access, like cPanel or Plesk, including username and password – obtained from hosting admin.

Is FTP backup of files also necessary?

How important are your files? If its a chance that your site files can be destroyed – through hosting failure, WordPress upgrade, or act of God – then it is wise to do an FTP backup of all files on the hosting server, as well as Database Backup to enable complete replication of entire website.

Replicate WordPress site

Once all your server files are backed up – downloaded by FTP to your hard drive – its as easy as transferring them back onto a server by FTP.

Then upload – Restore – your WordPress Database Backup using phpMyAdmin. WordPress Database Backup and Restore, can be initiated from phpMyAdmin in your site’s Control Panel – details below.

Using phpMyAdmin to Backup WordPress Database

• Go Login to your Control Panel
• Scroll menus for a reference to Databases – Click on phpMyAdmin link there

• phpMyAdmin homepage – Top left corner shows Database names, WordPress Database ends in “_wrdp1″ or similar. Click on the name of the database you would like to backup, see picture below
  

• The next screen appears, showing your database with tables revealed.
• Click Export on the top menus.

• All tables should be selected for Export by default, if not, select them all.

• On the same page, Scroll down
• Tick [] Save as file, Select .”zipped“
• Click [Go] button to download your Database in Zip file – Save to your desktop

All done!

The downloaded Zip file, bearing the name of the database .zip, should be kept safe, as this file will be needed, in order to:

Restore WordPress Database

Additional information:
WordPress Backups – WordPress Codex
Backing Up Your Database – WordPress Codex