How to flag duplicate rows

Hello experts,

How do I mark duplicate rows (BY ID) in data services data flow..

Example below..I want to add a flag = 1 as seen below so that when I load data there will be only one record per ID.

ID001 DALLAS  SALVATION ARMY
ID001 HOUSTON MISSION   --> flag = 1
ID001 AUSTIN  GOODWILL  --> flag = 1
ID002 SEATTLE GOODWILL
ID003 DULUTH  MISSION
ID003 ATLANTA SA        --> flag = 1

Auto correct load in template table is not working.

Thanks
Ann