Count of how many times id occurs in table SQL regexp - sql

Question

Hi I have a redshift table of articles that has a field on it that can contain many accounts. So there is a one to many relationship between articles to accounts.
However I want to create a new view where it lists the partner id's in one column and in another column a count of how many times the partner id appears in the articles table.
I've attempted to do this using regex and created a new redshift view, but am getting weird results where it doesn't always build properly. So one day it will say a partner appears 15 times, then the next 17, then the next 15, when the partner id count hasn't actually changed.
Any help would be greatly appreciated.
SELECT partner_id,
COUNT(DISTINCT id)
FROM (SELECT id,
partner_ids,
SPLIT_PART(partner_ids,',',i) partner_id
FROM positron_articles a
LEFT JOIN util.seq_0_to_500 s
ON s.i < regexp_count (partner_ids,',') + 2
OR s.i = 1
WHERE i > 0
AND regexp_count (partner_ids,',') = 0
ORDER BY id)
GROUP BY 1;

Answer 1

Let's start with some of the more obvious things and see if we can start to glean other information.
Next GROUP BY 1 on your outer query needs to be GROUP BY partner_id.
Next you don't need an order by in your INNER query and the database engine will probably do a better job optimizing performance without it so remove ORDER BY id.
If you want your final results to be ordered then add an ORDER BY partner_id or similar clause after your group by of your OUTER query.
It looks like there are also problems with how you are splitting a partnerid from partnerids but I am not positive about that because I need to understand your view and the data it provides to know how that affects your record count for partnerid.
Next your LEFT JOIN statement on the util.seq_0_to_500 I am pretty sure you can drop off the s.i = 1 as the first condition will satisfy that as well because 2 is greater than 1. However your left join really acts more like an inner join because you then exclude any non matches from positron_articles that don't have a s.i > 0.
Oddly then your entire join and inner query gets kind of discarded because you only want articles that have no commas in their partnerids: regexp_count (partner_ids,',') = 0
I would suggest posting the code for your util.seq_0_to_500 and if you have a partner table let use know about that as well because you can probably get your answer a lot easier with that additional table depending on how regexp_count works. I suspect regex_count(partnerids,partnerid) exampleregex_count('12345,678',1234) will return greater than 0 at which point you have no choice but to split the delimited strings into another table before counting or building a new matching function.
If regex_count only matches exact between commas and you have a partner table your query could be as easy as this:
SELECT
p.partner_id
,COUNT(a.id) AS ArticlesAppearedIn
FROM
positron_articles a
LEFT JOIN PARTNERTABLE p
ON regexp_count(a.partnerids,p.partnerid) > 0
GROUP BY
p.partner_id
I will actually correct myself as I just thought of a way to join a partner table without regexp_count. So if you have a partner table this might work for you. If not you will need to split strings. It basically tests to see if the partnerid is the entire partnerids, at the beginning, in the middle, or at the end of partnerids. If one of those is met then the records is returned.
SELECT
p.partner_id
,COUNT(a.id) AS ArticlesAppearedIn
FROM
PARTNERTABLE p
INNER JOIN positron_articles a
ON
(
CASE
WHEN a.partnerids = CAST(p.partnerid AS VARCHAR(100)) THEN 1
WHEN a.partnerids LIKE p.partnerid + ',%' THEN 1
WHEN a.partnerids LIKE '%,' + p.partnerid + ',%' THEN 1
WHEN a.partnerids LIKE '%,' + p.partnerid THEN 1
ELSE 0
END
) = 1
GROUP BY
p.partner_id