The CARDINALITY function returns the number of elements in a list.
CARDINALITY returns an integer value giving the number of elements in the list specified by ListExpression.
A common use of this function is to determine the number of fields in a list before iterating over them.
-- Determine the number of F1 fields in the message.
-- Note that the [ ] are required
DECLARE CountF1 INT CARDINALITY(OutputRoot.XMLNS.Data.Source.F1[]);
-- Determine the number of fields called F1 with the value 'F12' in the message.
-- Again note that the [ ] are required
DECLARE CountF1F12 INT
CARDINALITY(SELECT F.* FROM OutputRoot.XMLNS.Data.Source.F1[] AS F
where F = 'F12');
-- Use the value returned by CARDINALITY to refer to a specific element
-- in a list or array:
-- Array indices start at 1, so this example refers to the third-from-last
-- instance of the Item field
Body.Invoice.Item[CARDINALITY(Body.Invoice.Item[]) - 2].Quantity