How to make unique random alphanumeric sequence in SQL Server

Question

I want to make unique random alphanumeric sequence to be the primary key for a database table.

Each char in the sequence is either a letter (a-z) or number (0-9)

Answer 1

NewID() Function will generate unique numbers.So i have incremented them with loop and picked up the combination of alpha numeric characters using Charindex and Left functions

;with list as 
    (
        select 1 as id,newid() as val
             union all
        select id + 1,NEWID()
        from    list   
        where   id + 1 < 100
    ) 
    select ID,left(val, charindex('-', val) - 2) from list
    option (maxrecursion 0)