Get the number of unique values in each non-empty column in each non-empty table in a MySQL database. Handy for getting a rough idea of what your data looks like. I'm sure there's a more Ruby-ic way to do this, but this gets the job done.

gistfile1.rb

c = ActiveRecord::Base.connection
c.execute("SHOW TABLES").each do |t|
  table = t[0]
  c.execute("SELECT COUNT(*) FROM `#{table}`").each do |n|
    count = n[0]
    next if count == 0
    puts
    puts "#{table.upcase}: #{count}"
    collist = c.execute("DESC `#{table}`").map {|x| x[0]}
                                          .select { |x| !['created_at', 'updated_at', 'id', 'visible'].include?(x) }
    count_list = c.execute("SELECT COUNT(DISTINCT " + collist.join('), COUNT(DISTINCT ') + ") FROM `#{table}`").first
    collist.each_with_index do |col, index|
      if count_list[index] > 0
        puts "#{col}: #{count_list[index]}"
      end
    end 
  end
end