>1. 1.query is slower than 2.query. Why ?

Because actually creating the file on disk is the slowest part in this case, and creating a table with one field is a lot faster than creating a table with a lot of fields.

>2. Rushmore optimization of second query is executed wrongly. Why ?

Why do you say that? On a quick glance, it looked right to me.

>3. How can I solve rushmore optimization problem ?

What do you mean?

Tamar