Keep the rows with the largest or smallest values

CREATE TABLE orders AS SELECT * FROM (VALUES
  (1,  'Alice Ng',      'north', DATE '2026-01-03', 120.00, 'widget', 'a|b',   '{"channel":"web","items":[1,2]}'),
  (2,  'alice ng',      'north', DATE '2026-01-05',  80.50, 'gadget', 'b',     '{"channel":"shop","items":[3]}'),
  (3,  'Bob  Okafor',   'south', DATE '2026-01-05', 300.00, 'widget', 'a|c',   '{"channel":"web","items":[4,5,6]}'),
  (4,  'Carla Díaz',    'east',  DATE '2026-01-09',  NULL,  'gizmo',  NULL,    '{"channel":"web","items":[]}'),
  (5,  'Bob Okafor',    'south', DATE '2026-01-12',  45.25, 'gadget', 'c',     '{"channel":"phone","items":[7]}'),
  (6,  'Dev Patel',     'west',  DATE '2026-01-12', 510.00, 'widget', 'a',     '{"channel":"web","items":[8,9]}'),
  (7,  'Carla Diaz',    'east',  DATE '2026-01-20',  99.99, 'gizmo',  'b|c',   '{"channel":"shop","items":[10]}'),
  (8,  'Dev Patel',     'west',  DATE '2026-02-02', 510.00, 'widget', 'a',     '{"channel":"web","items":[8,9]}'),
  (9,  'Eve Larsen',    NULL,    DATE '2026-02-03',  15.00, 'gadget', NULL,    '{"channel":"web","items":[11]}'),
  (10, 'Alice Ng',      'north', DATE '2026-02-10', 220.00, 'gizmo',  'a|b|c', '{"channel":"phone","items":[12,13]}')
) t(order_id, customer, region, order_date, amount, product, tags, meta);

-- largest three amounts; the two 510.00 orders tie, so the later order date comes first
CREATE TEMP TABLE largest AS
SELECT order_id, amount, order_date FROM orders ORDER BY amount DESC NULLS LAST, order_date DESC LIMIT 3;
-- smallest two amounts, leaving out the order with no amount
CREATE TEMP TABLE smallest AS
SELECT order_id, amount FROM orders WHERE amount IS NOT NULL ORDER BY amount ASC LIMIT 2;
-- the single largest: the tie at 510.00 goes to the later order date
CREATE TEMP TABLE winner AS
SELECT order_id FROM orders ORDER BY amount DESC NULLS LAST, order_date DESC LIMIT 1;
SELECT * FROM largest;
SELECT * FROM smallest;
SELECT CASE WHEN ((SELECT list(order_id ORDER BY amount DESC, order_date DESC) FROM largest) = [8, 6, 3] AND (SELECT order_id FROM winner) = 8 AND (SELECT list(order_id ORDER BY amount) FROM smallest) = [9, 5]) THEN 'as expected' ELSE error('the largest three were not orders 8, 6 and 3 with 8 first, or the smallest two were not orders 9 and 5') END AS verdict;