有没有办法返回所有记录，其中特定列上的下一条记录的值来自上一条记录 + 1？

Question

I have table with 2 columns: Year And Month.

Example:

Year    |     Month
1. 2020            9
2. 2020            8
3. 2020            7
4. 2020            5
5. 2020            4

I don,t have record for 06.2020, so as a result i want to get only all the results before the break: 1,2,3

Example 2:
1. 2020 12
2. 2020 11
3. 2020 10
4. 2020 09
5. 2020 08
6. 2020 07
7. 2020 05
8. 2020 04
9. 2020 02

I want to get as result: 1,2,3,4,5,6

Answer 1

One method is:

select t.*
from (select t.*,
             sum(case when next_yyyymm <> year * 12 + month + 1 then 1 else 0 end) over (order by year desc, month desc) as num_misses
      from (select t.*,
                   lead(year * 12 + month) over (order by year, month) as next_yyyymm
            from t
           ) t
      ) t
where num_misses = 0;

This adds up the number of misses up to a given year/month combination. It returns the rows with no missing month.

Here is a db<>fiddle showing both examples.