排序方式上多列ID降序不同postrges

Question

SELECT impressions.* 
FROM impressions 
WHERE impressions.user_id = 2 
    AND impressions.action_name = 'show' 
    AND (impressions.message IS NOT NULL) 
GROUP BY impressionable_id, impressionable_type 

我想從表中選擇那些在impressionable_id和impresssionable_type訂貨獨特的降ID的所有過去的印象，並獲得最後10

爲了解釋這種進一步

id, impressionabale_type, impressionable_id, action_name 

50012, assignment, 2, show 
50011, assignment, 1, show 
50010, person, 1, show 
50009, assignment, 1, show 
50008, person, 5, show 
50007, person, 4, show 
50006, person, 3, show 
50005, person, 1, show 
50004, person, 1, show 
50003, person, 2, show 
50002, person, 2, show 
50001, person, 1, show 
50000, person, 1, show 

理想我想這

50012, assignment, 2, show 
50011, assignment, 1, show 
50010, person, 1, show 
50008, person, 5, show 
50007, person, 4, show 
50006, person, 3, show 
50003, person, 2, show 

我已經試過次方ct和group by但是我的sql知識最好是公平的。

我得到

PG::GroupingError: ERROR: column "impressions.id" must appear in the GROUP BY clause or be used in an aggregate function 

有人可以提供一些線索，請

Answer 1

也許Th1將滿足您的需求：

SELECT t2.* 
FROM (
    SELECT DISTINCT impressionable_id, impressionabale_type 
    FROM impressions 
    WHERE impressions.action_name = 'show' 
) t1, LATERAL (
    SELECT * 
    FROM impressions 
    WHERE (t1.impressionable_id,t1.impressionabale_type) = (impressionable_id,impressionabale_type) 
    ORDER BY id DESC 
    LIMIT 1 
) t2 
ORDER BY id DESC 
LIMIT 10 

這將找到的impressionable_id和impressionable_type併爲每個都是獨一無二的組合的子查詢會在LATERAL子查詢中找到id中最大的那一行。

Answer 2

select * 
from (
    select *, 
     row_number() over (
      partition by impressionable_id, impressionable_type 
      order by id desc 
     ) as rn 
    from impressions 
    where 
     user_id = 2 
     and action_name = 'show' 
     and message is not null 
) s 
where rn = 1