Erlang with mnesia and json

I’m starting with Erlang

And I have some problem to understand how Erlang work with mnesia and with Json

So I have to mnipulate some data of msesia ( select and update) using Erlang

Then I want to retreive some data from json using Erlang (in fact I have to do a function with Erlang and in this function I have to parse this file) has someone an idea to solve these problems

thank you in advance for your help

first I need to manipulate data from mnesia using Erlang ( like in sql : select and update) then I have to manipulate other data from json using Erlang