FOREIGN KEY (tenant_id, author_id) REFERENCES users ON DELETE SET NULL (author_id)
And this:
FOREIGN KEY (tenant_id, author_id) REFERENCES users (tenant_id, user_id) ON DELETE SET NULL (author_id)
Produce an identical outcome.
The absence of a column list on the former causes the system to look at the primary key for the named table and use its column list - which is (tenant_id, user_id), same as the later explicit version.
