“An invasion of Armies can be resisted, but not an idea whose time has come.”
- Victor Hugo
This query is easy to understand. It uses an IN List to find all Employees who are in Dept_No 100 or Dept_No 200.
What is going on with this IN List? Why in the world are their duplicates in there? Will this query even work? What will the result set look like? Duplicate values are ignored here. We got the same rows back as before, and ...