SQL Server table-valued function problems

Question

Just got another query that I'm pulling what remaining hair I have left out over here.

I have 4 tables ( Product , Customers , Orders and Order Details ) I need to create a valued table function that passes Country Name to the function. I also need the function to join my Customers table with my Orders table. I ideally want to filter Countries by Order Date. So I'd like to able to Select from the function that tells me orders from a certain country within a certain date range.

So far I've tried the following with not much success:

USE sample;
GO
CREATE FUNCTION Orders_By_Country (@Country VARCHAR(50))
    RETURNS TABLE
    AS RETURN (SELECT Customers.Country, Customers.CompanyName
                    FROM Customers
                   WHERE Customers.Country = Orders.ShipCountry
                 AND Country = @Country);

I don't have a Country column in my Orders table so maybe that is why it's not working. Not sure how to join these two. Orders and Customers share CustomerID as a relation but trying that gave me an error as well.

Any ideas? I have to go to bed now, but I'll check back first thing in the morning.

Thanks

Answer 1

If you want to use the Orders table to make decisions or if you want to return one or multiple columns from that table in your TVF, you need to join to it!

CREATE FUNCTION Orders_By_Country (@Country VARCHAR(50))
    RETURNS TABLE
    AS RETURN 
       (SELECT Customers.Country, Customers.CompanyName
        FROM Customers
        INNER JOIN Orders ON Orders.CustomerId = Customers.CustomerId
        WHERE 
            Customers.Country = Orders.ShipCountry
            AND Country = @Country);

or then you might not need it at all - seeing that you have a Country column on the Customers table:

CREATE FUNCTION Orders_By_Country (@Country VARCHAR(50))
    RETURNS TABLE
    AS RETURN 
       (SELECT Customers.Country, Customers.CompanyName
        FROM Customers
        WHERE 
            Customers.Country = @Country);