Jump to content

Exists operator

Jim S-T

Recommended Posts


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?








Link to comment
Share on other sites

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.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Create New...