Find Gaps in a Numeric Sequence

SELECT
  t1.id + 1 AS missing_id
FROM
  your_table t1
LEFT JOIN
  your_table t2 ON t1.id + 1 = t2.id
WHERE
  t2.id IS NULL
ORDER BY
  missing_id
LIMIT 1;

How it works: This query identifies the first missing ID in a sequence. It performs a `LEFT JOIN` on the table itself, checking if `t1.id + 1` exists in `t2.id`. If `t2.id` is `NULL` for a given `t1.id`, it signifies a gap, meaning `t1.id + 1` is missing from the table.