"Lennart" <erik.lennart.jonsson (AT) gmail (DOT) com> wrote

But, as Lee pointed out there is no particular relationship between an
autoincrement column in one table and an autoincrement coulmn in a different
table. So, at the semantic level, there is nothing "natural" about the
joins that the OP presented as a case study.

Saying that a join across two unrelated columns both with name "id" is
"natural" is really stretching a point, in my book.

David Cressey wrote:
Yes, you are right. But it does not make sence to do any kind of join
between two tables with autoincrement columns, and natural is less
typing than other joins.

The OP's query was about the cardinality of the resulting table and
whether an inner join or a natural join is used is irrelevant.

You seem to put some value in the word natural? AFAIK it is only a
syntactical construction in sql.



/Lennart