If you test and delete a lot of plugins, then overtime your wordpress database will be cluttered with table from these plugins. It really good measure tidying up your database to make it clean from table that no longer needed. Moreover you will get more free space that you can use in your web server.
There are several ways to clean up database. You can pick any techniques you want to clean the database.
Tell WordPress to Fix Database
You can set WordPress so it can fix database automatically. This will be helpful if you cannot login because the database is broken. Since version 2.9, WordPress supports fixing data by adding a command in wp-config.php file. Open the file using your favorite text editor and add the text below:
Using Plugins to Fix Database
There are several plugins that you can use to fix and optimize the database. Two of them are Clean Options and WP-Optimize.
Clean Options plugin will traverse through your database to search for table that no longer used then delete it. While with WP-Optimize plugin, you can both clean and optimize database. What WP-Optimize will do is deleting post revision, spam comments, and unapproved comments with just a few clicks.
To optimize database performance automatically, you can use WP Database Optimizer. With this plugin, you can create a schedule to do optimization.
Fixing Database via PHPMyAdmin
If you like to directly open the database and search for table that need to be optimized from the database, then you can use PHPMyAdmin. Open your PHPMyAdmin and choose the database. Then look at the Overhead column, click Check tables having overhead to pick all the table with overhead. Then pick Optimize Table from drop-down menu in the right to begin optimization.