One of the most underrated features of SQL is the set operators:
IMO in some cases set operators are much more readable then joins. For example, when we need to get records that appear in both tables. Yep, it’s a job for the
INNER JOIN. But it our tables have only one column (just list of emails returned by a view or subquery) then I’d vote for the set operators. Let’s look at some examples.
UNION operators combines two sets (read tables or query results) together. We’ve used it already to create virtual tables:...