Sql to select Max event on two grouped by one column - sql

Question

I have the following table :
+----------+------+
| country | event |
+----------+-----------+
| usa | running |
| usa | running |
| usa | running |
| canada | running |
| Canada | running |
| usa | javline |
| canada | javline |
| canada | javline |
| canada | javline |
+----------+-----------+
I want to get the following out by sql query:
USA | Running | 3
Canada | Javline | 3
i tried using the following query on MS sql server :
select country, case when c > 1 then null else event end event
from (select country, [ModelName], recs, count(*) over (partition by event, recs ) c,
row_number() over (partition by country order by recs desc) rn
from (select country, event, count(*) recs
from table
group by country, event) )
where rn = 1
order by 1
But I get an error :
Msg 102, Level 15, State 1, Line 12
Incorrect syntax near ')'.
Any pointers to correct solution is appreciated. Thanks.

Answer 1

You need to put an alias on your subquery:
select
country,
case when c > 1 then null else event end event
from (
select -- No event here
country,
[ModelName],
recs,
count(*) over (partition by event, recs ) c,
row_number() over (partition by country order by recs desc) rn
from (
select country, event, count(*) recs -- No ModelName here
from [table]
group by country, event
) x -- You need to put an alias here
)t -- and here
where rn = 1
order by 1
Note that the above query will still produce errors:
Invalid column name 'ModelName'.
Invalid column name 'event'.
This is because ModelName is not included in your innermost subquery and event is not included in the outermost subquery.
Based on your sample data, you can use this query to achieve the desired result:
;WITH Cte AS(
SELECT Country, Event, COUNT(*) AS CC
FROM [Table]
GROUP BY Country, Event
)
,CteRowNumber AS(
SELECT *,
RN = ROW_NUMBER() OVER(PARTITION BY Country ORDER BY CC DESC)
FROM Cte
)
SELECT Country, Event, CC
FROM CteRowNumber
WHERE RN = 1

Answer 2

You could do it using window function inside a cte:
-- this counts a number per each country and event
with q as(
select country,event,
row_number() over(partition by country,event order by country) r
from your_table t
)
--this takes only the maximum of them
select *
from q
where r=(select max(r)
from q q2
where q2.country=q.country)
Result:
| country | event | r |
|---------|---------|---|
| canada | javline | 3 |
| usa | running | 3 |