Hi.
First of all: Why do you keep two different tables to store the questions?
Im my opinion, you would have much less trouble by puting them all in one table, and using a field for telling them apart. Like this:
create table questions
(
qid integer unsigned not null auto_increment,
qdesc varchar(255),
qtype char(10),
primary key(qid)
)
Where qtype can be either: 'EASY' or 'DIFFICULT'
( You can use any code you like for classifying the questions, like 0 and 1. I personally prefer to use values that are understandable)
With a table structure like this you would only have to update the records with question type = 'EASY' with 80% or more incorrect answers to type = 'DIFFICULT'
I am suppposing you have another table where you store the answers or the results, and that you can calculate the % of wrong answers.
HTH
-Gio-