#oracle
see <http://archive.adaic.com/standards/83rat/html/ratl-03-07.html>

PL/SQL is based on ADA programming language -- which does not allow "empty" statements. You have to specify NULL key word to signify an empty statement.

That's why in PL/SQL exception handlers we often do something like this:

BEGIN
...
EXCEPTION 
    WHEN OTHERS THEN
        NULL;
END;