There used to be a difference, if I am correct. Many years ago, we had to rewrite a lot of implicit joins before we could upgrade MySQL because they changed the precedence of tables in implicit joins between major versions. I couldn't easily find this reference, but it was well over 10 years ago.

EDIT: 10 years ago... lol it was over 20! http://download.nust.na/pub6/mysql/doc/refman/5.0/en/join.ht... search for 5.0.12 on this page.