如何在SQL中为那些供应商提供的所有零件的供应商找到供应商编号？

Question

I am trying to find the SNO for the Supplier that supplied all parts that is supplied that by another by Supplier.

For example, I have

(S1, P1, 100), 
(S1, P2, 200), 
(S2, P1, 300), 
(S2, P2, 100),
(S3, P1, 400),
(S4, P1, 100), 
(S4, P2, 200)

So I am trying to find the SNO of the suppliers that supplied all the parts supplied by S2 not one part. Therefore, the answer should be S1 & S4 but I could not get the SQL Query to solve this. I hope I could get some help.

Answer 1

this is how I achieved the result:

create table MyTable (
  Supplier varchar(20),
  Part varchar(20),
  SomeOrder int
)

insert into MyTable values 
('S1', 'P1', 100),
('S1', 'P2', 200), 
('S2', 'P1', 300), 
('S2', 'P2', 100),
('S3', 'P1', 400),
('S4', 'P1', 100), 
('S4', 'P2', 200)
---------------------------

-- temporary table to store all parts of a supplier
CREATE TABLE #tmp (Part varchar(20))

-- put your desired provider here
declare @Supplier varchar(20) = 'S2'

-- select all parts of this supplier
insert into #tmp
select Part from MyTable where Supplier = @Supplier

-- count how many parts this supplier has
declare @partCount int
select @partCount = count(*) from #tmp

-- select all suppliers that have all the parts (i.e. count = @partCount)
select innerTbl.Supplier from (
    select m.Supplier, m.Part
    from MyTable m
    inner join #tmp t on t.Part = M.Part
  ) innerTbl
 group by innerTbl.Supplier
 having Count(innerTbl.Supplier) = @partCount 
 and innerTbl.Supplier <> @Supplier

Answer 2

You can do this without temporary tables. Assuming there are no duplicates in your table:

select sp.supplier
from supplierparts sp join
     supplierparts sp2
     on sp.part = sp2.part and sp2.supplier = 2
group by sp.supplier
having count(*) = (select count(*) from supplierparts sp3 where sp3.supplier = 2);

If you wanted exact equality (that is, supplying P3 would invalidate the supplier), then:

select sp.supplier
from supplierparts sp left join
     supplierparts sp2
     on sp.part = sp2.part and sp2.supplier = 2                    
group by sp.supplier
having count(*) = (select count(*) from supplierparts sp3 where sp3.supplier = 2) and
       count(*) = count(sp2.part);