Haskell functions are pure, which means they can only access/use what is in their parameters, so unless you pass in some extra context (typically using a monad or an effect), you do not have access to the "outside world".
I'm used to Boost.Bind and similar, so was thinking a scenario where you bind the database connection parameter and pass the resulting function to something else.
As the sibling pointed out though, I now get that the result would be "tainted" so to speak.
A database connection would operate either in IO (the generic "i am now talking to an unreliable outside world") monad, or some more specific monad.
In this case you can think of a monad a bit like a computational context. If one is not present, you simply cannot[^1] instruct a Haskell program to perform those operations in a type safe way even if you give it a valid database connection identifier.
[1] Well, you can, but if you do you're explicitly taking away all the safeguards that Haskell introduces, and it would never pass code review.
