There is a constraint in SS, but it doesn't work the same way as it does in Oracle - i.e., you can't specify it to CASCADE.
In SS, the table being deleted from is aliased as "deleted" - likewise, for an insert or update the table is aliased "inserted" - so the code would look like this.
CREATE TRIGGER mydelete_trigger
ON parent_table
FOR DELETE
AS
DELETE FROM child_table WHERE iparentid = deleted.iid
Insanity: Doing the same thing over and over and expecting different results.