[Exim] general queston: quoting in SQL-statements

Hi,

I have a general question to the list regarding quoting:

I almost never see a ${quote_X:Y} in SQL-samples posted to
this mailing-list while I spent quite some time quoting
all externally defined data in my lookups...

What would list-members consider good practice in this field?
Or does exim employ special "magic" (like for example php does...)
when putting $local_part etc... in sql queries?

        Chris