Query to fetch distinct rows with below requirement - sql

Question

Sample date in the table:
+--------+---------+---------+--------------+-----------+------------+---+
| School | Class | Student | Student desc | Section | Date | |
+--------+---------+---------+--------------+-----------+------------+---+
| ABC | Grade 2 | Stud 1 | AAA | Mango | 5/12/2015 | 1 |
| DEF | Grade 2 | Stud 1 | AAA | Mango | 12/25/2018 | |
| DEF | Grade 2 | Stud 1 | AAA | Orange | 9/8/2016 | |
| GHI | Grade 3 | Stud 2 | BBB | Apple | 12/28/2016 | 2 |
| JKL | Grade 3 | Stud 2 | BBB | Pear | 12/19/2016 | |
| ABC | Grade 2 | Stud 3 | CCC | Guava | 12/28/2016 | 3 |
| GHI | Grade 3 | Stud 4 | DDD | StarFruit | 9/8/2018 | 4 |
+--------+---------+---------+--------------+-----------+------------+---+
Ideally mapping should be 1 student is only get assigned to one section in a class.
I need to build the query to fetch the data to meet below requirement:-
Irrespective of the School need to show the distinct data for those students which get assigned to multiple sections within same class.
+--------+---------+---------+--------------+----------+------------+
| School | Class | Student | Student desc | Section | Date |
+--------+---------+---------+--------------+----------+------------+
| DEF | Grade 2 | Stud 1 | AAA | Mango | 12/25/2018 |
| DEF | Grade 2 | Stud 1 | AAA | Orange | 9/8/2016 |
| GHI | Grade 3 | Stud 2 | BBB | Apple | 12/28/2016 |
| JKL | Grade 3 | Stud 2 | BBB | Pear | 12/19/2016 |
+--------+---------+---------+--------------+----------+------------+
Below is the query that provides the correct data if school information is fetched:
select distinct a.class
,a.student
,a.Stud desc
,a.section
,to_date(max(a.date),'MM-DD-YYYY')"Date"
from Table1 a,
( select class
,student
,count(distinct section) cot
from Table1 c
where 1=1
and class is not null
and incoming_qty >= 1
group by class
,student
Having count(distinct section) > 1
) b
where 1=1
and a.class = b.class
and a.student=b.student
and b.cot > 1
and b.class is not null
and a.incoming_qty_new >= 1
group by a.class,a.student,a.Stud desc,a.section
order by a.class,a.student,a.Stud desc,a.section;
But query not working as per expectation while trying to fetch the school detail.
Please suggest.

Answer 1

Here is example of analytic functions usage for your data. Try to extend it for your specific case.
WITH t(School, Class, Student, StudentDesc, SectionName, Dates) AS
(
SELECT 'ABC','Grade 2','Stud 1','AAA','Mango',date'2015-05-12' FROM dual UNION ALL
SELECT 'DEF','Grade 2','Stud 1','AAA','Mango',date'2018-12-25' FROM dual UNION ALL
SELECT 'DEF','Grade 2','Stud 1','AAA','Orange',date'2016-09-08' FROM dual UNION ALL
SELECT 'GHI','Grade 3','Stud 2','BBB','Apple',date'2016-12-28' FROM dual UNION ALL
SELECT 'JKL','Grade 3','Stud 2','BBB','Pear',date'2016-12-19' FROM dual UNION ALL
SELECT 'ABC','Grade 2','Stud 3','CCC','Guava',date'2016-12-28' FROM dual UNION ALL
SELECT 'GHI','Grade 3','Stud 4','DDD','StarFruit',date'2018-09-08' FROM dual
)
SELECT *
FROM (
SELECT t.*,
COUNT(DISTINCT SectionName) OVER (PARTITION BY Class, Student) AS cntStudentSections,
ROW_NUMBER() OVER (PARTITION BY Class, Student ORDER BY Dates) AS StudentRowNumber
FROM t
)
WHERE cntStudentSections > 1 AND StudentRowNumber = 1;

Answer 2

You can use analytic functions:
select t1.*
from (select t1.*,
count(*) over (partition by class, student, section) as cnt
from table1 t1
) t1
where cnt >= 2;