Yes Adobe Campaign... How do we do it using xml updates?

I somehow have some entries in my schema where PK Attribute is NULL.I created the workflow by querying those rows and added Delete Data Step.. but records wont get deleted.. Error message is PK cant be NULL.                

I have a requirement where i want to change the Primary Key from internal to Auto PK.. How do i do it?If i change the key and update database structure .. i get this error message;08:00:51 - PGS-220000 PostgreSQL error: ERROR:  could not create unique index "schemaName_id" DETAIL:  Key (ischemaid)=(...