如何在sql中将字符串转换为数组并连接到另一个表

SELECT
  user_id,
  SUBSTRING_INDEX(SUBSTRING_INDEX(order_ids, ',', numbers.n), ',', -1) AS order_id
FROM
  (SELECT 1 AS n UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4) numbers
  INNER JOIN users ON CHAR_LENGTH(order_ids) - CHAR_LENGTH(REPLACE(order_ids, ',', '')) >= numbers.n - 1
ORDER BY
  user_id, order_id;

SELECT *
FROM orders
WHERE order_id IN (
  SELECT
    SUBSTRING_INDEX(SUBSTRING_INDEX(order_ids, ',', numbers.n), ',', -1) AS order_id
  FROM
    (SELECT 1 AS n UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4) numbers
    INNER JOIN users ON CHAR_LENGTH(order_ids) - CHAR_LENGTH(REPLACE(order_ids, ',', '')) >= numbers.n - 1
);