sortByItem
A single sort key within a sort by clause. Consists of an expression term identifying the value to sort on and an optional direction. Multiple sort items form a lexicographic ordering.
Examples
Sort by date, ascending (default)
from [Encounter] E sort by E.period.start
Sort by date, descending
from [Observation] O sort by O.effective desc
Multiple sort items
from [Observation] O sort by O.effective desc, O.id asc
EBNF
sortByItem : expressionTerm sortDirection? ;