Grant Fritchey dodges the important questions:
First response, also a joke, was the question at the title of this post:
What is the preferred operator when joining tables: Hash Match, Nested Loops or Merge?
While my immediate response to this question is, yes. Meaning, they’re all preferred, situationally. I decided to expand on that a bit.
I completely agree with Grant: there is no single best operator. If there were, database companies wouldn’t have multiple options. That said, in an ideal world, all joins would be merge joins; in our fallen world, nested loops and hash matches often prove superior second-best alternatives.