SQLite count, group and order by count
SELECT foo, count(bar) FROM mytable GROUP BY bar ORDER BY count(bar) DESC;
The group by statement tells aggregate functions to group the result set by a column. In this case "group by bar" says count the number of fields in the bar column, grouped by the different "types" of bar.
A better explanation is here: http://www.w3schools.com/sql/sql_groupby.asp