QBJoin

var query = foundset.getQuery();
query.result.add(query.columns.name, "name");
query.where.add(query.columns.orderdate.isNull)

foundset.getQuery().joins

var query = datasources.db.example_data.person.createSelect();
/** @type {QBJoin<db:/example_data/person>} */
var join1 = query.joins.add('db:/example_data/person')
join1.on.add(query.columns.parent_person_id.eq(join1.columns.person_id))
/** @type {QBJoin<db:/example_data/person>} */
var join2 = query.joins.add('db:/example_data/person')
join2.on.add(join1.columns.parent_person_id.eq(join2.columns.person_id))

query.where.add(join2.columns.name.eq('john'))
foundset.loadRecords(query)

var query = datasources.db.example_data.person.createSelect();
	query.where.add(query.joins.person_to_parent.joins.person_to_parent.columns.name.eq('john'))
	foundset.loadRecords(query)

var subquery = datasources.db.example_data.order_details.createSelect();

	var query = datasources.db.example_data.orders.createSelect();
	query.where.add(query
		.or
			.add(query.columns.order_id.not.isin([1, 2, 3]))

			.add(query.exists(
					subquery.where.add(subquery.columns.orderid.eq(query.columns.order_id)).root
			))
		)

	foundset.loadRecords(query)

foundset.getQuery().getColumn('orderid')

foundset.getQuery().getColumn('orderid', 'opk')