In practical applications, you pretty much always have synthetic row IDs in cases where there aren't any natural ones.
I think it would be more helpful if you could give a specific example of a simple SQL query that does not map nicely to a relational expression, since it's kind of hard to discuss the specifics in these vague terms.
I don't understand what you are looking for. There is no specific SQL query I know of that could not expressible in relational calculus in some manner. But that also has nothing to do with the discussion.
The discussion is about why SQL became the standard. Being first is not it. It wasn't first. It was second, but QUEL came along hot on its heels before SQL established itself. It was approximately another decade after that before SQL solidified dominance.
- Was there a specific technical reason to choose SQL over QUEL/LINUS?
- Was there a specific human reason to choose SQL over QUEL/LINUS?
- Was it just random chance and if we were to do it all over again we are just as likely to see QUEL/LINUS become the standard instead?
I think it would be more helpful if you could give a specific example of a simple SQL query that does not map nicely to a relational expression, since it's kind of hard to discuss the specifics in these vague terms.