If you set the ‘group by’ or ‘categorise by’ properties to have RainPro automatically cross-total (e.g. for Towercharts) it defaults to sorting the categories (ascending numbers or alphabetically).

chSet 'style' 'asis'

The ‘asis’ option simply takes the unique group ids ‘cast in order of appearance’ and is probably what you want if you already used an SQL query to order the data.