Question

This can certainly be done using a simple script and reading the database.
I am interested to know if the same is possible using some MySQL query.

Table Schema :

+--------+-------------------------------+
| doc_id | doc_title                     |
+--------+-------------------------------+
| 40692  | hello                         |
| 13873  | isaac                         |
| 37739  | einstei                       |
| 36042  | cricket                       |
| 96249  | astronaut                     |
| 81931  | discovery                     |
| 28447  | scooby                        |
| 99632  | popeye                        |
+--------+-------------------------------+

Here doc_id is a random number between 1 to 99999 , the distribution is sparse. I would want to know longest ( or all of the longest ) unused number ranges in my mysql table.
i.e. if 71000 to 83000 is the longest such range, there will be no record having doc_id lying between these two values.

Answer 1

How about something like this

SELECT t1.doc_id,
       MAX(t1.doc_id-IFNULL(t2.doc_id,0)) AS difference
FROM `table` t1
    LEFT JOIN `table` t2 ON t1.doc_id>t2.doc_id
    LEFT JOIN `table` t3 ON (t1.doc_id>t3.doc_id AND t3.doc_id>t2.doc_id)
WHERE t3.doc_id IS NULL
GROUP BY t1.doc
ORDER BY difference DESC