Exists operator

[Jim S-T]

Hi,

I am slowly making my way through the SQL tutorial and have got a bit stuck on the exists tutorials. This is one of the examples, but I do not understand why they have used SELECT ProductName.

SELECT supplierid, SupplierName
FROM Suppliers
WHERE EXISTS (SELECT ProductName FROM Products WHERE SupplierId = Suppliers.supplierId AND Price < 20);

 

When running SQL it provides 2 columns, supplier ID and Supplier Name as per the 1st line. I have replaced ProductName with * and get the same results, is it a best practice thing, or have I been getting worked up over not much as they just needed something to fill the space?

 

Thanks

 

Jim

 

 

 

[justsomeguy]

Which columns are selected inside the exists subquery is totally irrelevant, they aren't even used.  I always do SELECT * for those.  The only thing that matters is if a row was returned at all, the number or values of columns aren't even considered.

[Jim S-T]

Thanks