example UPDATE My_Table WHERE 1=2

It is clear that will be no locks on the rows.
But there can be TM lock on the table to prevent DDL.
It seems logical that TM lock could be put on table only on the first real update.
But probaly it put in the begining no matter if it will not update anything.
If update does full scan of big table and it last very long and in the middle of update somebody drops filed you are using in your query.
But if apropriate index exists then probably first index can be scaned and if key is found only then TM is put on the table.