startingClause
Specifies the initial accumulator value for an aggregate clause. May be a simple literal, a quantity, or a parenthesized expression. When omitted, the accumulator starts as null.
Examples
Starting from zero
from [Observation] O aggregate Total starting 0: $total + O.value
Starting from an empty string
from Items I aggregate Result starting '': $total + I.label + ', '
Starting from a parenthesized expression
from [Observation] O aggregate Count starting (0 as Integer): $total + 1
EBNF
startingClause
: 'starting' (simpleLiteral | quantity | ('(' expression ')'))
;