how to check the number continure or not in postgreSQL?

Hi I have database like:

id  |  lownumber | highnumber | content
---------------------------------------
1   |   10       |   13       | text
2   |    14      |    19      |  book
3   |    6       |     9      |  table
...

I want to check the lownumber and highnumber contine or not. I mean the previous highnumber + 1 equal the next line lownumber or not? how to do that in postgresql?

Answer

You can get the exceptions using lag():

select t.*
from (select t.*, lag(highnumber) over (order by id) as prev_highnumber
      from t
     ) t
where lownumber <> prev_highnumber + 1;

Note: “previous” is ambiguous. I don’t know from the question if it refers to the previous row based on id or lownumber. If the latter, then change the order by.