Boolean operator for comparing against one or multiple expressions.
SELECT 'elastic' <=> null AS "equals"; equals --------------- false
SELECT null <=> null AS "equals"; equals --------------- true
SELECT last_name l FROM "test_emp" WHERE emp_no <> 10000 ORDER BY emp_no LIMIT 5;
SELECT last_name l FROM "test_emp" WHERE emp_no < 10003 ORDER BY emp_no LIMIT 5;