Query based on multiple rows and multiple columns - sql

Question

Database : Azure SQL server 2019, .net core 3.0
I'm using stored procedure for querying data.
--Table Structure
create table yourtable
(
id int,
class int,
islab bit,
isschool bit
);
insert into yourtable
values (1, 1, 1, 1),
(1, 2, 1, 1),
(1, 3, 1, 1),
(2, 1, 1, 0),
(2, 2, 1, 1),
(2, 3, 1, 1)
Now if I want a query to return all unique Id's where class = 1 and 2 and islab = 1 and isschool = 1, it should return only Id =1 because
a) Id=1 has both classes i,e (1,2) and in both classes islab = 1 and isschool = 1
b) Id=2 is not true for this condition because in classes 1 value for isschool = 0
Can you help me write this query? Currently I'm getting all row for input classes than in c# using list check all conditions. It's working but I want do all in SQL
Also I think using cursor in stored procedure I can have same result as in C# but in C# it's easy as we have Collection and various methods like intersect between lists and so on.

Answer 1

Assuming that islab and isschool are actually a bit (as bool doesn't exist in SQL Server), one method would be to use a HAVING with conditional aggregation. So, for the first one, you would do the following:
SELECT id
FROM dbo.yourtable
WHERE islab = 1
AND isschool = 1
GROUP BY id
HAVING COUNT(CASE class WHEN 1 THEN 1 END) = 1
AND COUNT(CASE class WHEN 2 THEN 1 END) = 1;

Answer 2

The question is not clear, but based on your expected output, I think you want a query that, for a given set of classes, finds the ids where there are no records with isschool = 0 or islab = 0. You can do this with a NOT EXISTS condition:
WITH mytab AS
(
SELECT *
FROM yourtable
WHERE class IN (1,2,3) -- Change this line to get your 3 different outputs
)
SELECT DISTINCT id
FROM mytab t1
WHERE NOT EXISTS
(
SELECT *
FROM mytab t2
WHERE t1.id = t2.id
AND (t2.islab = 0 OR t2.isschool = 0)
)
For class IN (1,2) this returns id 1.
For class IN (2,3) this returns ids 1 and 2.
For class IN (1,2,3) this returns id 1.
The CTE limits to the classes we want to consider. The subquery in the NOT EXISTS finds ids that should be eliminated because either isschool = 0 or islab = 0.
An alternative way of doing this, using a LEFT JOIN instead of the NOT EXISTS condition is:
WITH mytab AS
(
SELECT *
FROM yourtable
WHERE class IN (1,2,3) -- Change this line to get your 3 different version
)
SELECT DISTINCT t1.id
FROM mytab t1 LEFT OUTER JOIN mytab t2
on t1.id = t2.id AND (t2.islab = 0 OR t2.isschool = 0)
WHERE t2.id is null