I'm new to MySQL and I'm having trouble trying to figure out how to solve the following problem:

1 - I have a table with data about some people, including a name, a number code and a category for each one.

*Let's supose "JOHN DOE" is one of them, his number code is "1111" and his category is "A"; "FOO" is another one, with number code "2222" and category "B"; and "BAR" is another one, number code "3333" and category "A".*

2 - Everyone in category "A" was suposed to fill out a form which filled a second table in my database. In this table, the reference to the responsible for each answer is his/her number code. Each person could also answer the form more than one time.

**The problem is:** Now I need a table that shows me who answered the form and who did't.

**PS:** Let's call the database "data\_base", the first table "people" (with columns "name", "num\_code" and "category") and the second table "answers" (with columns "num\_code" and "answer").

Could someone help me?