# File lib/thinking_sphinx/attribute.rb, line 91
    def to_select_sql
      return nil unless include_as_association? && available?
      
      separator = all_ints? || all_datetimes? || @crc ? ',' : ' '
      
      clause = columns_with_prefixes.collect { |column|
        case type
        when :string
          adapter.convert_nulls(column)
        when :datetime
          adapter.cast_to_datetime(column)
        when :multi
          column = adapter.cast_to_datetime(column)   if is_many_datetimes?
          column = adapter.convert_nulls(column, '0') if is_many_ints?
          column
        else
          column
        end
      }.join(', ')
      
      clause = adapter.crc(clause)                          if @crc
      clause = adapter.concatenate(clause, separator)       if concat_ws?
      clause = adapter.group_concatenate(clause, separator) if is_many?
      clause = adapter.downcase(clause)                     if insensitive?
      
      "#{clause} AS #{quote_column(unique_name)}"
    end