Query don't return the right result - sql

Question

I have a POST table, a ACTION table and ACTION_TYPE table, I explain the ACTION table contains all the actions that were made by users, and the table ACTION_TYPE contains the actions details for example the ACTION whose ID = 4 has ACTION_TYPE_ID = 1 for POST_ID 6, which mean an action was made for post number 50, we can have many actions for one post_id
the POST table
id title content user_id
---------- ---------- ---------- ----------
1 title1 Text... 1
2 title2 Text... 1
3 title3 Text... 1
4 title4 Text... 5
5 title5 Text... 2
6 title6 Text... 1
the ACTION_TYPE table
id name
---------- ----------
1 updated
2 deleted
3 restored
4 hided
the ACTION table
id post_id action_type_id date
---------- ---------- -------------- -----
1 1 1 2017-01-01
2 1 1 2017-02-15
3 1 3 2018-06-10
4 6 1 2019-08-01
5 5 2 2019-12-09
6 2 3 2020-04-27
7 2 1 2020-07-29
8 3 2 2021-03-13
So i would like to know the last action are made for each post sometimes i would like to get teh last action made by specific action_type and user for each post.
here is my query
select actions, count(*) as cnt
from(
select ac.post_id as action_post_id, max(ac.date) as max_date,
case
when ac.action_type_id is not null then act.name
end as actions,
case
when p.user_id is not null then u.name
end as user_name
from action ac
left join post p on ac.post_id = p.id
left join user u on p.user_id = u.id
left join action_type act on ac.action_type_id = act.id
where p.user_id = 1
and act.name in ('restored','deleted','updated')
group by ac.post_id, case when ac.action_type_id is not null then act.name end , case when p.user_id is not null then u.full_name end
)
group by actions
;
so here is one probleme i want to groupe by post_id but it ask me to add cases too so i get the following error:
/ORA-00979. 00000 - "not a group by expression/
when i delete the cases from group by
but when i use this query i get false result
here the result i get
actions user_name cnt
---------- ---------- -----------
updated ERIC 2
deleted ERIC 2
restored ERIC 2
so here the result expected to be
actions user_name cnt
---------- ---------- -----------
updated ERIC 2
deleted ERIC 1
restored ERIC 1
the sum must equal 4 but i'm geting 6 it's like if it brings more than one action per post
Important ! when i use simple query to check manualy actions the sum equal 4
Best regards

Answer 1

You can use:
SELECT MAX(t.name) AS action_name,
MAX(u.name) AS user_name,
COUNT(*) AS number_posts
FROM users u
INNER JOIN post p
ON (u.id = p.user_id)
INNER JOIN (
SELECT post_id,
MAX(action_type_id) KEEP (DENSE_RANK LAST ORDER BY "DATE", id)
AS action_type_id
FROM action
GROUP BY post_id
) a
ON (p.id = a.post_id)
INNER JOIN action_type t
ON (t.id = a.action_type_id)
GROUP BY
u.id,
t.id
Which, for the sample data:
CREATE TABLE users (id, name) AS
SELECT 1, 'Eric' FROM DUAL;
CREATE TABLE POST ( id, title, content, user_id) AS
SELECT 1, 'title1', 'Text...', 1 FROM DUAL UNION ALL
SELECT 2, 'title2', 'Text...', 1 FROM DUAL UNION ALL
SELECT 3, 'title3', 'Text...', 1 FROM DUAL UNION ALL
SELECT 4, 'title4', 'Text...', 5 FROM DUAL UNION ALL
SELECT 5, 'title5', 'Text...', 2 FROM DUAL UNION ALL
SELECT 6, 'title6', 'Text...', 1 FROM DUAL;
CREATE TABLE ACTION_TYPE ( id, name ) AS
SELECT 1, 'updated' FROM DUAL UNION ALL
SELECT 2, 'deleted' FROM DUAL UNION ALL
SELECT 3, 'restored' FROM DUAL UNION ALL
SELECT 4, 'hided' FROM DUAL;
CREATE TABLE ACTION ( id, post_id, action_type_id, "DATE") AS
SELECT 1, 1, 1, DATE '2017-01-01' FROM DUAL UNION ALL
SELECT 2, 1, 1, DATE '2017-02-15' FROM DUAL UNION ALL
SELECT 3, 1, 3, DATE '2018-06-10' FROM DUAL UNION ALL
SELECT 4, 6, 1, DATE '2019-08-01' FROM DUAL UNION ALL
SELECT 5, 5, 2, DATE '2019-12-09' FROM DUAL UNION ALL
SELECT 6, 2, 3, DATE '2020-04-27' FROM DUAL UNION ALL
SELECT 7, 2, 1, DATE '2020-07-29' FROM DUAL UNION ALL
SELECT 8, 3, 2, DATE '2021-03-13' FROM DUAL;
Outputs:
ACTION_NAME
USER_NAME
NUMBER_POSTS
restored
Eric
1
updated
Eric
2
deleted
Eric
1
fiddle