dbUnquoteIdentifier() returns a list of objects
of the same length as the input.
For an empty character vector this function returns a length-0 object.
The names of the input argument are preserved in the output.
When passing the first element of a returned object again to
argument, it is returned unchanged (but wrapped in a list).
Passing objects of class Id should also return them unchanged (but wrapped in a list).
(For backends it may be most convenient to return Id objects
to achieve this behavior, but this is not required.)
An error is raised if plain character vectors are passed as the
For any character vector of length one, quoting (with
then unquoting then quoting the first element is identical to just quoting.
This is also true for strings that
contain special characters such as a space,
or quotes used to mark strings
if the database supports this.
Unquoting simple strings (consisting of only letters) wrapped with
and then quoting gives the same result as just quoting.