So when it comes to hard coding within PL/SQL, I'd say I'd agree with Steven Feuerstein. I agree with most of his standards, and his article on this is concise.
In the other corner, Jeff Kemp raises an excellent point about hard coding in SQL. We worked on a complex project together once where hard coding of certain literals was important - and done correctly. Commenting never goes astray. This example is way out of context so it's hard to illustrate, but if I may:
SELECT something FROM my_table WHERE entity_type = 123 /* XYZ type */ AND entity_id = :my_bind_parameter;Where entity_type contains the value that will never change, and hence Jeff's adage - "do not change this code"
Also note Narendra's comment on Jeff's article - be very careful about the use of cursor_sharing = FORCE in these scenarios.
I just wanted to highlight these two related articles.