Selecting only rows that have matching column values - sql

Question

so I have the task of returning the a companies information if and only if ALL of their products have been discontinued.
I have a Suppliers and a Products table. The Suppliers table has a ProductID column and the Products table has a ProductID and a Discontinued column that stores a bit (1 being true or 0 being false).
If anyone has a solution to this, that would be a life saver.
EDIT: the query I'm working with would be something like this
select
s.CompanyName, p.ProductName, p.Discontinued
from
Suppliers s
join
Products p on s.SupplierID = p.SupplierID
and the output would be something like this
CompanyName ProductName Discontinued
-------------------------------------------------------------
Exotic Liquids Chai 0
Exotic Liquids Chang 0
Exotic Liquids Aniseed Syrup 0
New Orleans Cajun Delights Chef Anton's Cajun Seasoning 0
New Orleans Cajun Delights Chef Anton's Gumbo Mix 1
Grandma Kelly's Homestead Grandma's Boysenberry Spread 0
Grandma Kelly's Homestead Uncle Bob's Organic Dried Pears 0
Grandma Kelly's Homestead Northwoods Cranberry Sauce 0
Tokyo Traders Mishi Kobe Niku 1
Tokyo Traders Ikura 0
but I only want it to return the suppliers with all discontinued products

Answer 1

I'm going out on a limb here, but I think you're trying to JOIN two tables on the ProductID.
If that's the case, then you SQL query would look something like this:
SELECT a.ProductID, b.Discontinued FROM Suppliers a
LEFT JOIN Products b ON (a.productID = b.productID)
WHERE b.Discontinued = true

Answer 2

select Suppliers.SupplierID, CompanyName from Suppliers
inner join Products on
Products.SupplierID = Suppliers.SupplierID
where Discontinued = 1
and Products.SupplierID not in
(select SupplierID from Products where Discontinued = 0)
group by Suppliers.SupplierID, CompanyName

Answer 3

Become a better developer in every language you use. Stop trying to do everthing at once. Break the problem into digestible pieces. And learn how to post good questions. You have a query question - how do you expect others to understand your issue and supply useful suggestions without knowing your schema and understanding how you use it. Sure - it's fairly simple in this case but a script that generates your tables, populates them with sample data, and includes whatever you have tried encourages others to respond.
So the first step is to answer the question "which supplies provide only discontinued products". Apparently you have all the information you need in Product. Something like:
select P.SupplierID from dbo.Products as P
group by P.SupplierID
having min(cast(P.Discontinued as tinyint)) = 1
order by P.SupplierID;
I think that is correct but it is still a guess. Sometimes a bit column gets "used" in opposition to the name. What does that do? For each group generated by the group by clause (supplier ID), it will determine the min value of Discontinued (casting is necessary since you cannot use min/max with bit). For a supplier with all discontinued products, that column must be 1 for all associated rows. Since 1 > 0, that means that all products of a supplier are discontinued. Grouping also gives us a distinct set of rows.
Now that you know how to generate a distinct set of SupplierID values, you should be able to apply that to any other query to get information about those suppliers. You can join, use IN, use exists - try all three if you want to really make this a learning experience.