Hello,

I want to delete rows in a table where the primary key is not
referenced. something like:
DELETE FROM mytable WHERE primary_key NOT IN (SELECT theref FROM
referertable)

Is such a request internaly optimized ? (I suppose there is some
flag already in a row to note if it is referenced)
can I simply do a DELETE FROM mytable without any other test and
only those rows that are not referenced would be deleted ?
is there a better way to do that ?

please help
Benedicte