detect fragmented tables

Hello

Before working with optimizer, Stethoscope and Tomograph , first I have to defragment the fragmented tables. How to detect fragmented tables ? Write a script that reads heapsize column ?

select * , ( heapsize / 1021/1024/1024) as giga from sys.storage heapsize ORDER BY DESC LIMIT 20; What do you think ?

or a more specific sql query by reading the column "count ", " typewidth ", " ColumnSize " and " heapsize " ?

thank

Pierre