DELETE ADJACENT DUPLICATES

hallow

i wont to delete appearance in table of mine when data appear more then one time

example

itab before

<b>field num</b>

100 aa

100 bb

200 cc

200 dd

itab after

<b>field num</b>

100 aa

200 cc

<b>i reward</b>

regars

i try with

DELETE ADJACENT DUPLICATES FROM itab

but its not working

Regards