dividing the string into sub strings

Question

HI all,

Here i am retrieving mobile numbers from database like 919849098490(means 12 digit).And i am getting hundreds of numbers to a variable.

so i need to divide those numbers into 100 numbers into a string with commas.

means if i have 245 mobile numbers then i need to divide those numbers to three strings like first 100 numbers to str1,next hundred numbers to str2 and remaining 45 numbers to str3.

above situation is an example.

if i have mobile numbers like 850 then i have 9 string variables.


I want in a line(12 digit numbers string) also appended a comma for every 12 digit number except before first number and after last number.

Means 919849098490,919849098490,919849098490 here three 12 digit numbers are there and separated with two commas only.

i want like

str1 =919849098490,919849098490,919849098490

thank you.