I'm trying to return just non-null `diff_review` values > 1 and so far this has been my result:

[![diff_review with null value](https://i.stack.imgur.com/RokMu.png)](https://i.stack.imgur.com/RokMu.png)

This is the query that generated this:

```
select review_number
  , review_number - lag(review_number, 1) over (partition by organization_id order by review_number) as diff_review from applications
where organization_id = 25144
and kind = 'annual_review'
and review_number is not null
order by diff_review desc

```

I can't use `...and diff_review is not null` since you can't use aliases in `where` clauses, but I found out today you also can't use windowing functions in `where` clauses either.

This is the first time I've ever used windowing in SQL (I hadn't even heard of it until an hour ago) so I'm still very green at this. I'd appreciate someone clueing me in thanks!!!