maybe help you:

http://www.xaprb.com/blog/2005/12/06/find-missing-numbers-in-a-sequence-with-sql/




In a table I have records with id's 2,4,5,8. How can I receive a list with values 1,3,6,7. I have tried in this way

>
>SELECT t1.id + 1
>FROM table t1
>WHERE NOT EXISTS (
>    SELECT *
>    FROM table t2
>    WHERE t2.id = t1.id + 1
>)
>
>but it's not working correctly. It doesn't bring all available positions.
>
>Is it possible without creating another table?
>

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