SQL & PL/SQL

Hi Friends,

Oracle 11.2.0.1
Windows XP Prof.

Two questions, but almost same nature :

1.Is there any formula by which we can get the total count of prime numbers for a given number; i mean suppose I says 10, it means it should return 3; i.e. there are total 3 prime number between 1-10.

Here I can use a function which will say me that a given number is prime or not, and i will loop up to that given number. But, this is not actually a Formula, its kind of calculation. I am just looking a fixed matehematical formula for it; if it exists or not. If exists, then how that PL/SQL block will looks like.

2.Suppose I wish to get 50 prime numbers (starting from 1), then what will be the 50th prime number, i mean upto which highest number my calculation will expanded.

If possible, this should also be based upon a fixed formula.

Not actually a business requirement, but my nephew (student of class 9th) asked me these questions. I said him, neither I am student of maths nor that much knowledgeable in PL/SQL.

I asked him, why you are looking these formulas. He said, just these questions raised in my mind and curious to know that is there a fixed formula in maths exists or not. I said him, "Have you asked from your Maths teacher?" He said "Yes, sir told me, that there is no such a fixed mathematical formula, because there is no fixed gap in their ranges, what you says?"

I thought, let me write here.

Regards
Girish Sharma