Exists
The exists operator is Boolean-valued function that tests whether
a subquery has a non-empty result and has the form
exists ( <query> )
where <query> is any query.
It is a syntactic shortcut for
len([<query>]) != 0
Examples
Simple example showing true for non-empty result
# spq
values exists (values 1,2,3)
# input
# expected output
true
EXISTS is typically used with correlated subqueries but they are not yet supported
# spq
let Orders = (values {product:"widget",customer_id:1})
SELECT 'there are orders in the system' as s
WHERE EXISTS (
SELECT 1
FROM Orders
)
# input
# expected output
{s:"there are orders in the system"}