Hugo Kornelis gives an example of a red flag:
This anniversary edition is hosted by Brent Ozar. And his chose topic is: query red flags. Things that make you groan when you open a query and see them in the code. I’m sure there will be a ton of posts, because there are so many. I myself could probably fill a book with things I consider a red flag (and someone else would then point out that my queries have things that they consider red flags, but that is another discussion).
But let’s focus on just one thing in this post.
Hugo selects the case when all query joins are LEFT OUTER joins. Especially when the logic of the query mandates INNER joins.
Meanwhile, if all of your query joins are RIGHT OUTER joins, you’re just chaotic evil.