How to retrieved specific data from three different tables - sql

Question

i have 3 tables, every table contains the different information of student(e.g personal detail, course detail, academic details etc), in which students have 4 different category(SC, ST, OBC and Gen). i want to retrieve the student list according to there category and Plus2Percentage.
eg.
1. i want to retrieve 2 students from SC category whose Plus2Percentage is >= 60,
then
i want to retrieve 2 students from ST category whose Plus2Percentage is >= 65,
then
i want to retrieve 1 students from OBC category whose Plus2Percentage is >= 60,
then
i want to retrieve 2 students from All 4(SC, ST, OBC and Gen) category whose Plus2Percentage is >= 70, but in this i dont want to retrieve those students info who has been already retrieved.(e.g those two student from SC Category who has been already retrieved from very step and so on from the ST OBC category)
[Table1]:
| Roll No | Applicant Name| Gender | Category | Father's Name |
|------------|---------------|------------|------------|----------------|
| 001 | A | M | SC | as |
| 002 | B | F | ST | hg |
| 003 | C | F | ST | yj |
| 004 | D | M | OBC | uy |
| 005 | E | F | SC | bn |
| 006 | F | M | OBC | kl |
| 007 | E | F | Gen | bn |
| 008 | F | M | OBC | vg |
| 009 | E | F | Gen | gh |
| 010 | F | M | SC | we |
|------------|---------------|------------|------------|----------------|
[Table2]:
| ID | Semester | Major | Applied Course|
|------------|---------------|------------|---------------|
| 001 | 1 | English | B.A |
| 002 | 1 | English | B.A |
| 003 | 1 | History | B.A |
| 004 | 1 | botany | B.Sc |
| 005 | 1 | Hindi | B.A |
| 006 | 1 | History | B.A |
| 007 | 1 | Maths | B.A |
| 008 | 1 | Hindi | B.A |
| 009 | 1 | History | B.A |
| 010 | 1 | Pol.Science| B.A |
|------------|---------------|------------|---------------|
[Table3]:
| ID |Plus2Percentage|
|------------|---------------|
| 001 | 60 |
| 002 | 65 |
| 003 | 70 |
| 004 | 73 |
| 005 | 87 |
| 006 | 91 |
| 007 | 59 |
| 008 | 78 |
| 009 | 88 |
| 010 | 57 |
|------------|---------------|-
[Output]:
| Roll No |Plus2Percentage| Category |
|------------|---------------|-----------|
| 005 | 87 | SC |
| 001 | 60 | SC |
| 003 | 70 | ST |
| 002 | 65 | ST |
| 006 | 91 | OBC |
| 009 | 88 | Gen |
| 008 | 78 | OBC |
|------------|---------------|-----------|
2 Students from SC Category whose Percentage is above or equal to 60%.
Roll No 005 and 001 from sc.
2 Students from ST Category whose Percentage is above or equal to 65%.
Roll No. 002 and 003 from st.
1 Students from OBC Category whose Percentage is above or equal to 60%.
Roll No. 006 from OBC
and
2 Students from all category whose percentage is above 70%, but excluding previously retrieved students.
Roll No. 009 and 008 from all over
Previously working code,when i was retrieving data from1 table ,instead of 3 Tables:
WITH PRIMARY_CHOICE AS (
SELECT
RollNo,
ApplicantName,
FatherName,
Gender,
Major,
Category,
Plus2Percentage
FROM (
SELECT
RollNo,
ApplicantName,
FatherName,
Gender,
Semester,
Major,
AppliedCourse,
Category,
Plus2Percentage,
row_number() over (partition by Category, Semester, Major, AppliedCourse order by Plus2Percentage desc) as rn
FROM [College Management System].[dbo].[ApplicantPersonalDetail]
) as T
WHERE
rn <= CASE
WHEN Category='SC' AND Semester='1' AND AppliedCourse= 'B.A' AND Plus2Percentage >= '60' THEN '2'
WHEN Category='ST' AND Semester= '1' AND AppliedCourse= 'B.A' AND Plus2Percentage >= '65'THEN '2'
WHEN Category='OBC' AND Semester= '1' AND AppliedCourse= 'B.A' AND Plus2Percentage >= '60' THEN '1'
ELSE 0
END
)
SELECT
RollNo,
ApplicantName,
FatherName,
Gender,
Major,
Category,
Plus2Percentage
FROM PRIMARY_CHOICE
UNION ALL
SELECT
RollNo,
ApplicantName,
FatherName,
Gender,
Major,
Category,
Plus2Percentage
FROM (
SELECT
RollNo,
ApplicantName,
FatherName,
Gender,
Semester,
Major,
AppliedCourse,
Category,
Plus2Percentage,
row_number() over (partition by Semester, Major1, AppliedCourse order by Plus2Percentage desc) as rn
FROM [College Management System].[dbo].[ApplicantPersonalDetail] x
WHERE NOT EXISTS (
select 1 from primary_choice y
where x.RollNo = y.RollNo
)
) AS T2
WHERE
rn <= 2
AND Semester = #semester
AND AppliedCourse = 'B.A'
AND Plus2Percentage >= 70
order by Plus2Percentage desc

Answer 1

SELECT RollNo, Plus2Percentage, Category
FROM TABLE1 a
INNER JOIN Table3 b on a.rollno=b.id
WHERE a.category='SC' and b.Plus2Percentage>=60
That should be enough for the first three bullets. The fourth one is a matter of either setting up the predicate or encapsulating a union of the first three and then doing a NOT IN.
Although I do feel it difficult to believe that someone who knows enough SQL to use ROW_NUMBER cannot troubleshoot a JOIN.

Answer 2

I have achieved the output but the query cost is high, if you have lots of data it populating every mins into your database than this query might not support the execution time.
I have used CTE table and UNION clauses for generating your output -
I have not used your table2 because there is no data required from that table in the output or is not dependent on table2
SQL SELECT CODE - you can replace your table and column names accordingly -
EDIT AFTER THE COMMENTS :- SOLUTION IS CHANGED INTO A STROED PROCEDURE READING DATA FROM TABLE VARIABLE
CREATE PROCEDURE usp_SelectCategorywiseData
AS
BEGIN
SET NOCOUNT ON;
DECLARE #tbl_LIST TABLE (RollNo int, [Plus2Percentage] int, Category varchar(10));
WITH CTE AS
(
SELECT A.RollNo, P.Percentage AS [Plus2Percentage], A.Category
, row_number() OVER (PARTITION BY A.Category ORDER BY P.Percentage DESC) AS Rank
FROM APPLICANT A INNER JOIN Plus2Percentage P ON A.RollNo = P.ID
)
INSERT INTO #tbl_LIST
SELECT RollNo, Plus2Percentage as [Plus2Percentage], Category
FROM CTE
WHERE rank <=
CASE
WHEN Category='SC' AND [Plus2Percentage] >= '60' THEN '2'
WHEN Category='ST' AND [Plus2Percentage] >= '60' THEN '2'
WHEN Category='OBC' AND [Plus2Percentage] >= '55' THEN '1'
ELSE 0
End
INSERT INTO #tbl_LIST
SELECT TOP 2 A.RollNo, P.Percentage as [Plus2Percentage], A.Category
FROM APPLICANT A INNER JOIN Plus2Percentage P ON A.RollNo = P.ID
WHERE Percentage > 70 and RollNo NOT IN (SELECT RollNo FROM #tbl_LIST) ORDER BY P.Percentage DESC
SELECT * FROM #tbl_LIST
END
What you will need to do is - create a temp table which will hold the data of first 5 records for SC, ST, OBC Category
Then Insert the records for all the category TOP 2 records order by percentage desc where Rollno is not in temp table. so that duplicates will be excluded and you will get the data.
ORDER BY SHOULD NOT BE USED AS ORDERING THE DATA CAN BE DONE LATER - IT COST THE EXECUTION TIME.
I will explain the USE of all the clauses here:
CTE - used to identify the row number (Ranking the records based on Percentage and grouping on Category)
Using CTE to select the data with individual conditional checks for Category and min. percentage.
Using UNION to get only distinct records as the final output.