SQLite 3.39

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CREATE TABLE IF NOT EXISTS events (
  `id`      TEXT PRIMARY KEY,
  `text`    TEXT
  );
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CREATE TABLE IF NOT EXISTS calendar (
  `id`       TEXT,
  `start`    TEXT
  );
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INSERT INTO events (`id`, `text`) VALUES
  ('id_1', 'hello'),
  ('id_2', 'world');
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INSERT INTO calendar (`id`, `start`) VALUES
  ('id_1', '2023-01-01'),
  ('id_1', '2023-06-01'),
  ('id_1', '2023-09-01'),
  ('id_1', '2023-10-01'),
  ('id_2', '2023-05-01'),
  ('id_2', '2023-08-29'),
  ('id_2', '2023-10-30'),
  ('id_2', '2023-11-30');
✓
select * from events
inner join calendar using (id)
where calendar.start > STRFTIME('%Y-%m-%d', 'now')
group by id


id
text
start


id_1
hello
2023-09-01

id_2
world
2023-08-29