That is, more specifically, in the expression: A, B LEFT JOIN C JOIN D CROSS JOIN E Only tables D and E are affected by the ordering constraint implied by the usage of the word CROSS. Re-ordering of all the tables is permitted so long as E is an inner table with respect to D. You are (apparently) interpreting the phrase **prevents the query optimizer from reordering the tables in the join** as meaning tables A, B, C, D, and E. However, this is not the case. The tables being cross joined and to which the ordering restriction applies are D and E only. You will also note that except for the specific case of a LEFT JOIN (where the ON clause specifies the conditions for the descent into the table on the RHS of the LEFT JOIN) an ON clause is merely syntactic sugar for a WHERE clause.