SQL Executioner

Instead of needing a tool like phpMyAdmin
or the mysql command line client to view and modify your WordPress database,
the SQL Executioner allows you to run arbitrary SQL queries against your
WordPress database from within the Admin. In many cases this allows you to bypass
the inherent limitations of the WordPress Admin interface, and use the full expressive
power of SQL to analyze and update your blog’s database.

To use simply install and visit the Tools > SQL Executioner page.

If you’re interested in contributing to the code behind this plugin, it’s also hosted on GitHub:
https://github.com/justincwatt/wp-sql-executioner