MySQL 8.0

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CREATE TABLE reserved (
  seats JSON
);

CREATE TABLE seats (
  id INT,
  name VARCHAR(100)
);

INSERT INTO reserved VALUES
  ('["276", "277", "278"]'),
  ('["276", "277", "279"]');
  
INSERT INTO seats VALUES
  (276, 'Name A'),
  (277, 'Name B'),
  (278, 'Name C');
SELECT r.seats, JSON_ARRAYAGG(s.name)
FROM reserved r INNER JOIN seats s ON JSON_SEARCH(r.seats, 'one', s.id) IS NOT NULL
GROUP BY r.seats


seats
JSON_ARRAYAGG(s.name)


["276", "277", "278"]
["Name A", "Name B", "Name C"]

["276", "277", "279"]
["Name A", "Name B"]


SELECT r.seats, JSON_ARRAYAGG(s.name)
FROM reserved r INNER JOIN seats s ON CONVERT(s.id, CHAR) MEMBER OF(r.seats)
GROUP BY r.seats


seats
JSON_ARRAYAGG(s.name)


["276", "277", "278"]
["Name A", "Name B", "Name C"]

["276", "277", "279"]
["Name A", "Name B"]


SELECT r.seats, JSON_ARRAYAGG(s.name)
FROM reserved r INNER JOIN seats s ON JSON_CONTAINS(r.seats, JSON_QUOTE(CONVERT(s.id, CHAR))) = 1
GROUP BY r.seats


seats
JSON_ARRAYAGG(s.name)


["276", "277", "278"]
["Name A", "Name B", "Name C"]

["276", "277", "279"]
["Name A", "Name B"]


SELECT JSON_ARRAYAGG(IFNULL(s.name, ''))
FROM reserved r, JSON_TABLE(
  r.seats,
  "$[*]" COLUMNS (
    id CHAR(50) PATH "$"
  )
) AS rr LEFT JOIN seats s ON rr.id = s.id
GROUP BY r.seats


JSON_ARRAYAGG(IFNULL(s.name, ''))


["Name A", "Name B", "Name C"]

["Name A", "Name B", ""]

seats	JSON_ARRAYAGG(s.name)
["276", "277", "278"]	["Name A", "Name B", "Name C"]
["276", "277", "279"]	["Name A", "Name B"]