I have a study assignment and I’ve been banging my head in the wall for at least a day now.
I’m totally new to this and just learning the basics.

This is my assignment:

Use union to combine these queries:

• Select customers whose city and postalcode both appear in suppliers table.
• Select customers whose name is at most five characters shorter than the longest supplier name.

Northwind database in question.

This is what i tried:

select customername, customers.city, customers.postalcode
from customers join suppliers
on customers.city = suppliers.city and customers.PostalCode = suppliers.PostalCode
union
select customername, customers.city, customers.postalcode
from customers
where length(customername) <
(select max(length(suppliername))
from suppliers)

Problem is that last “where clause”.
I know that the longest suppliername has 38 characters:

(select max(length(suppliername))
from suppliers) =38 characters

But i don’t know how to query that “at most five characters shorter”.

I get correct result set by querying:

where length(customername) > 33

but obviously that’s not what is asked for.

Thank you for the help 🙂