Android Sqlite : assign one column's values to another using ContentValues

I want to assign one column's values to another.

here is a query for it.

UPDATE contacts SET contactName=phone;

Here contactName and phone are two different columns.i am assigning phone column's values to contactName column.I can do this by using

db.rawQuery(query, null);

but if i want it to update it using

db.update(tableName, cValues, whereClause, whereArgs);

what should i put in Content values.If i put phone as a value then it will consider like

UPDATE contacts SET contactName="phone";

Help me to solve this issue. Any help will be appreciated.Thanks in advance