How to UPDATE row based on a row in same table

How you will update the Data of a table based on same table ??


update Table_DUMMY T1 
set COL_UPDT = (select T2.COL_FROM from Table_DUMMY T2 where T1.KEY=T2.KEY )  


Like the Facebook Page & join Group
https://www.facebook.com/DataStage4you
https://www.facebook.com/groups/DataStage4you
https://twitter.com/datastage4you
For WHATSAPP group , drop a msg to 91-88-00-906098