Count how many first and last entries in given period of time are equal - sql

Question

Given a table structured like that:
id | news_id(fkey)| status | date
1 10 PUBLISHED 2016-01-10
2 20 UNPUBLISHED 2016-01-10
3 10 UNPUBLISHED 2016-01-12
4 10 PUBLISHED 2016-01-15
5 10 UNPUBLISHED 2016-01-16
6 20 PUBLISHED 2016-01-18
7 10 PUBLISHED 2016-01-18
8 20 UNPUBLISHED 2016-01-20
9 30 PUBLISHED 2016-01-20
10 30 UNPUBLISHED 2016-01-21
I'd like to count distinct news that, in given period time, had first and last status equal(and also status equal to given in query)
So, for this table query from 2016-01-01 to 2016-02-01 would return:
1 (with WHERE status = 'PUBLISHED') because news_id 10 had PUBLISHED in both first( 2016-01-10 ) and last row (2016-01-18)
1 (with WHERE status = 'UNPUBLISHED' because news_id 20 had UNPUBLISHED in both first and last row
notice how news_id = 30 does not appear in results, as his first/last statuses were contrary.
I have done that using following query:
SELECT count(*) FROM
(
SELECT DISTINCT ON (news_id)
news_id, status as first_status
FROM news_events
where date >= '2015-11-12 15:01:56.195'
ORDER BY news_id, date
) first
JOIN (
SELECT DISTINCT ON (news_id)
news_id, status as last_status
FROM news_events
where date >= '2015-11-12 15:01:56.195'
ORDER BY news_id, date DESC
) last
using (news_id)
where first_status = last_status
and first_status = 'PUBLISHED'
Now, I have to transform query into SQL our internal Java framework, unfortunately it does not support subqueries, except when using EXISTS or NOT EXISTS. I was told to transform the query to one using EXISTS clause(if it is possible) or try finding another solution. I am, however, clueless. Could anyone help me do that?
edit: As I am being told right now, the problem lies not with our framework, but in Hibernate - if I understood correctly, "you cannot join an inner select in HQL" (?)

Answer 1

Not sure if this adresses you problem correctly, since it is more of a workaround. But considering the following:
News need to be published before they can be "unpublished". So if you'd add 1 for each "published" and substract 1 for each "unpublished" your balance will be positive (or 1 to be exact) if first and last is "published". It will be 0 if you have as many unpublished as published and negative, if it has more unpublished than published (which logically cannot be the case but obviously might arise, since you set a date threshhold in the query where a 'published' might be occured before).
You might use this query to find out:
SELECT SUM(CASE status WHEN 'PUBLISHED' THEN 1 ELSE -1 END) AS 'publishbalance'
FROM news_events
WHERE date >= '2015-11-12 15:01:56.195'
GROUP BY news_id

Answer 2

First of all, subqueries are a substantial part of SQL. A framework forbidding their use is a bad framework.
However, "first" and "last" can be expressed with NOT EXISTS: where not exists an earlier or later entry for the same news_id and date range.
select count(*)
from mytable first
join mytable last on last.news_id = first.news_id
where date between #from and #to
and not exists
(
select *
from mytable before_first
where before_first.news_id = first.news_id
and before_first.date < first.date
and before_first.date >= #from
)
and not exists
(
select *
from mytable after_last
where after_last.news_id = last.news_id
and after_last.date > last.date
and after_last.date <= #to
)
and first.status = #status
and last.status = #status;

Answer 3

NOT EXISTS to the rescue:
SELECT ff.id ,ff.news_id ,ff.status , ff.zdate AS startdate
, ll.zdate AS enddate
FROM newsflash ff
JOIN newsflash ll
ON ff.news_id = ll.news_id
AND ff.status = ll.status
AND ff.zdate < ll.zdate
AND NOT EXISTS (
SELECT * FROM newsflash nx
WHERE nx.news_id = ff.news_id
AND nx.zdate >= '2016-01-01' AND nx.zdate < '2016-02-01'
AND (nx.zdate < ff.zdate OR nx.zdate > ll.zdate)
)
ORDER BY ff.id
;