Data Explorer very likely what you’re looking for then! It allows you to write SQL queries against the database. You can see the basics in the Data Explorer Plugin topic. In short, visit your plugins page and enable it. Then you’ll see Data Explorer as a tab on the left site of the page. From there, just write the queries you need!
You may also wish to review What cool data explorer queries have you come up with? if you would like to see some sample queries.