SQL Subquery Issue: A Subtle Difference Leading to Unexpected Results

A reader, Dave, encountered a minor issue while testing a SQL subquery example from Vadim's book using the Northwind database on W3Schools. Dave's code differed slightly from the book's example, using '<' instead of '<=' and omitting '#'. Despite this, his scalar subquery returned zero, unlike the predecessor query in the book. This raises questions about how subtle differences in SQL queries can affect results.