title: Select multiple rows from one table
body: <p>I am trying to get random sets of rows from one table based on its rank.</p>
  
  <p>To be specific, I want to semi-randomly select players(rows) from a pool(table) to create a team. Each player is ranked from 0 to 100. The team is randomly picked from sets of ranks(Eg. 6 random players from top 20%, 8 random players from top 60%, and 6 players from top 100%)</p>
  
  <p>I've tried using union, but the calculation time increases linearly for each union statement added. (The pool is a result set of a query)</p>
  
  <p>Is there any other approach I should take other than union?</p>