I am working on a personal analytics project and I need to filter a SQL table. My SQL knowledge is very basic and moreover, I know that in Oracle but in this case I have to use SQLite and it seems to be quite different.
For example, suppose the table is
student physics chemistry maths history english
Brian 78 62 100 40 50
Bill 80 70 95 50 60
Brian 80 40 90 95 60
The table has repetition.
I asked a question earlier today, using the same example above, which would let me rank the subjects for each student.
How to RANK multiple columns of an entire table?
What I want to do now is find out which students had Maths in the top 3 among all subjects and group the table for each student. So the goal is to find out how many times did Brian have Maths in Top 3 of his scores.
IT WeiHan's answer to the previous question (https://www.db-fiddle.com/f/bjui5W1VWmHXcqKAhK5iBD/0 ) worked perfectly and displayed the rank of the subjects for each row. I used their answer and tried to modify it for this purpose.
with cte as (
select student,'physics' as class,physics as score from Table1 union all
select student,'chemistry' as class,chemistry as score from Table1 union all
select student,'maths' as class,maths as score from Table1 union all
select student,'history' as class,history as score from Table1 union all
select student,'english' as class,english as score from Table1
)
SELECT name,class,score,rnk,
(CASE
WHEN class = "maths" AND rnk <=3 THEN 1
ELSE 0
END) as maths_rank
FROM
(select student,class,score,RANK() OVER (partition by student order by score desc) rnk
from cte)
which gives a table like
name class score rnk maths_rank
Brian maths 100 1 1
I want to be able to count the maths_rank values or sum it (as it contains 1 or 0 values) and group the table on student name. I tried to count the maths_rank variable but that didn't work and resulted in errors. Please help me out with a solution.
If I understand correctly, you are on the right path. I think you just need a where clause:
with cte as (
select student,'physics' as class,physics as score from Table1 union all
select student,'chemistry' as class,chemistry as score from Table1 union all
select student,'maths' as class,maths as score from Table1 union all
select student,'history' as class,history as score from Table1 union all
select student,'english' as class,english as score from Table1
)
select t.*
from (select t.*,
rank() over (partition by student order by score desc) as subject_rank
from cte t
) t
where class = 'maths' and subject_rank <= 3;
Edit:
If you want the number of times maths was in the top 3, then:
select student, sum(case when class = 'maths' and subject_rank <= 3 then 1 else 0 end) as maths_top3
from (select t.*,
rank() over (partition by student order by score desc) as subject_rank
from cte t
) t
group by student;
Related
This question already has answers here:
Fetch the rows which have the Max value for a column for each distinct value of another column
(35 answers)
Closed 1 year ago.
I have table people containing people, their city and their money balance:
id city_id money
1 1 25
2 1 13
3 2 97
4 2 102
5 2 37
Now, I would like to select richest person from each city. How can I do that using Oracle SQL? Desired result is:
id city_id money
1 1 25
4 2 102
Something like that would be useful:
SELECT * as tmp FROM people GROUP BY city_id HAVING money = MAX(money)
You should be thinking "filtering", not "aggregation", because you want the entire row. You can use a subquery:
select p.*
from people p
where p.money = (select max(p2.money) from people p2 where p2.city_id = p.city_id);
You can use DENSE_RANK() analytic function through grouping by city_id(by using partition by clause) and descendingly ordering by money within the subquery to pick the returned values equal to 1 within the main query in order to determine the richest person including ties(the people having the same amount of money in each city) such as
SELECT id, city_id, money
FROM( SELECT p.*,
DENSE_RANK() OVER ( PARTITION BY city_id ORDER BY money DESC ) AS dr
FROM people p )
WHERE dr = 1
You can use RANK() as its flexible as you can get richest or top N richest
SELECT
id, city_id, money
FROM (
SELECT
p.* ,RANK() OVER (PARTITION BY city_id ORDER BY money DESC ) as rank_per_city
FROM
people p )
WHERE
rank_per_city = 1
I wrote this query for finding the highest score from 2 tables (Selected Item: StudentId and Score), and now I want to select some other data: (StudentName, StudentImage, ...) from other tables that must filter items using StudentId
my query returns:
StudentId HighScoreUser
-1 250
-2 100
-3 90
-4 80
-5 40
For showing data in a grid, I need the Student Name, ... so I must use StudentId to find the info for the specific user:
CREATE PROCEDURE SelectTopYear
AS
SELECT TOP 5 StudentId, ISNULL(SUM(Score),0) As HighScoreUser
FROM (SELECT StudentId, Score FROM tbl_ActPoint
UNION ALL
SELECT StudentId, Score FROM tbl_EvaPoint
) as T
GROUP BY StudentId ORDER BY HighScoreUser DESC
RETURN 0
You can use a CTE (or subquery) and JOIN:
WITH s as (
SELECT TOP 5 StudentId, ISNULL(SUM(Score),0) As HighScoreUser
FROM (SELECT StudentId, Score FROM tbl_ActPoint
UNION ALL
SELECT StudentId, Score FROM tbl_EvaPoint
) s
GROUP BY StudentId
ORDER BY HighScoreUser DESC
)
SELECT . . .
FROM s JOIN
othertable ot
ON s.StudentId = ot.StudentId;
Fill in the appropriate column names and table names.
I need to select the top score of all combined attempts by a player and I need to use a WITH clause.
create table scorecard(
id integer primary key,
player_name varchar(20));
create table scores(
id integer references scorecard,
attempt integer,
score numeric
primary key(id, attempt));
Sample Data for scorecard:
id player_name
1 Bob
2 Steve
3 Joe
4 Rob
Sample data for scores:
id attempt score
1 1 50
1 2 45
2 1 10
2 2 20
3 1 40
3 2 35
4 1 0
4 2 95
The results would simply look like this:
player_name
Bob
Rob
But would only be Bob if Rob had scored less than 95 total. I've gotten so far as to have the name and the total scores that they got in two columns using this:
select scorecard.player_name, sum(scores.score)
from scorecard
left join scores
on scorecard.id= scores.id
group by scorecard.name
order by sum(scores.score) desc;
But how do I just get the names of the highest score (or scores if tied).
And remember, it should be using a WITH clause.
Who ever told you to "use a WITH clause" was missing a more efficient solution. To just get the (possibly multiple) winners:
SELECT c.player_name
FROM scorecard c
JOIN (
SELECT id, rank() OVER (ORDER BY sum(score) DESC) AS rnk
FROM scores
GROUP BY 1
) s USING (id)
WHERE s.rnk = 1;
A plain subquery is typically faster than a CTE. If you must use a WITH clause:
WITH top_score AS (
SELECT id, rank() OVER (ORDER BY sum(score) DESC) AS rnk
FROM scores
GROUP BY 1
)
SELECT c.player_name
FROM scorecard c
JOIN top_score s USING (id)
WHERE s.rnk = 1;
SQL Fiddle.
You could add a final ORDER BY c.player_name to get a stable sort order, but that's not requested.
The key feature of the query is that you can run a window function like rank() over the result of an aggregate function. Related:
Postgres window function and group by exception
Get the distinct sum of a joined table column
Can try something like follows.
With (SELECT id, sum(score) as sum_scores
FROM scores
group by id) as sumScoresTable,
With (SELECT max(score) as max_scores
FROM scores
group by id) as maxScoresTable
select player_name
FROM scorecard
WHERE scorecard.id in (SELECT sumScoresTable.id
from sumScoresTable
where sumScoresTable.score = (select maxScoresTable.score from maxScoresTable)
Try this code:
WITH CTE AS (
SELECT ID, RANK() OVER(ORDER BY SumScore DESC) As R
FROM (
SELECT ID, SUM(score) AS SumScore
FROM scores
GROUP BY ID )
)
SELECT player_name
FROM scorecard
WHERE ID IN (SELECT ID FROM CTE WHERE R = 1)
I was asked this question in an interview, this the table
Roll | Sub | Marks
1 A 20
1 B 21
2 A 15
2 B 19
3 A 21
3 B 22
now i have to find the roll and marks 2nd highest marks obtained by the student
so i answered this :
declare #trytable table
(
roll int,
total int
)
insert #trytable
select Roll, SUM(Marks)
from Student
group by Roll
Select *
from #trytable t
where t.total in (select MAX(total) from #trytable where total not in ( select
MAX(total) from #trytable))
which is giving the correct answer but the interviewer wanted this to be done in single query
by not using the table variable
the result should be
Roll | Total Marks
1 41
so how can i do that ... please let me know
Below query gives the roll numbers who obtained 2nd highest marks summing the two subject marks.
SELECT TOP 1 Roll, Marks
FROM
(
SELECT DISTINCT TOP 2 Roll,
SUM(Marks) over (Partition by Roll) Marks
FROM
YourTable
ORDER BY marks DESC
) temp
ORDER BY Marks
OR
SELECT
DISTINCT Roll,
Marks,
SRANK
FROM
(
SELECT
Roll,
Marks,
DENSE_RANK() OVER( ORDER BY Marks DESC) AS SRANK
FROM
(
SELECT
Roll,
SUM(Marks) over (Partition by Roll) Marks
FROM YourTable
)x
)x
WHERE SRANK=2
If I understand you correctly, you just want to get the total score for the second highest student, and student is identified by roll? If so:
select roll, sum(Marks) from Student group by roll order by total limit 1,1;
Not 100% sure about the 1,1 - what you are saying is, I only want 1 row, and not the first.
It can also be done through simple query:
select Marks from trytable where N = (select count(distinct Marks) from trytable b where a.Marks <= b.Marks)
where N = any value
Or
SELECT Roll,Marks
FROM tableName WHERE Marks =
(SELECT MIN(Marks ) FROM
(SELECT TOP (2) Marks
FROM tableName
ORDER BY Marks DESC) )
You can use analytic functions like RowNumber()
select * from
(Select t.*, RowNumber() over (order by Total desc) as rownum from trytable )
where rownum = 2
Consider the following two tables:
student_id score date
-------------------------
1 10 05-01-2013
2 100 05-15-2013
2 60 05-01-2012
2 95 05-14-2013
3 15 05-01-2011
3 40 05-01-2012
class_id student_id
----------------------------
1 1
1 2
2 3
I want to get unique class_ids where the score is above a certain threshold for at least one student, ordered by the latest score.
So for instance, if I wanted to get a list of classes where the score was > 80, i would get class_id 1 as a result, since student 2's latest score was above > 80.
How would I go about this in t-sql?
Are you asking for this?
SELECT DISTINCT
t2.[class_ID]
FROM
t1
JOIN t2
ON t2.[student_id] = t1.[student_id]
WHERE
t1.[score] > 80
Edit based on your date requirement, then you could use row_number() to get the result:
select c.class_id
from class_student c
inner join
(
select student_id,
score,
date,
row_number() over(partition by student_id order by date desc) rn
from student_score
) s
on c.student_id = s.student_id
where s.rn = 1
and s.score >80;
See SQL Fiddle with Demo
Or you can use a WHERE EXISTS:
select c.class_id
from class_student c
where exists (select 1
from student_score s
where c.student_id = s.student_id
and s.score > 80
and s.[date] = (select max(date)
from student_score s1
where s.student_id = s1.student_id));
See SQL Fiddle with Demo
select distinct(class_id) from table2 where student_id in
(select distinct(student_id) from table1 where score > thresholdScore)
This should do the trick:
SELECT DISTINCT
CS.Class_ID
FROM
dbo.ClassStudent CS
CROSS APPLY (
SELECT TOP 1 *
FROM dbo.StudentScore S
WHERE CS.Student_ID = S.Student_ID
ORDER BY S.Date DESC
) L
WHERE
L.Score > 80
;
And here's another way:
WITH LastScore AS (
SELECT TOP 1 WITH TIES
FROM dbo.StudentScore
ORDER BY Row_Number() OVER (PARTITION BY Student_ID ORDER BY Date DESC)
)
SELECT DISTINCT
CS.Class_ID
FROM
dbo.ClassStudent CS
WHERE
EXISTS (
SELECT *
FROM LastScore L
WHERE
CS.Student_ID = L.Student_ID
AND L.Score > 80
)
;
Depending on the data and the indexes, these two queries could have very different performance characteristics. It is worth trying several to see if one stands out as superior to the others.
It seems like there could be some version of the query where the engine would stop looking as soon as it finds just one student with the requisite score, but I am not sure at this moment how to accomplish that.