To be more specific the "expr" in the "ON expr" following an outer join is bound into the particular descent (the LH table for a RIGHT OUTER JOIN and the RH table for a LEFT OUTER JOIN and to both tables for a both-ways OUTER JOIN) as compared to the expr in "ON expr" following an inner join which is merely syntactic sugar for an parethetically enlclosed AND term tacked on to the projection WHERE clause. table1 JOIN table2 does not in any way imply a cross join unless there are absolutely no constraints specified in the WHERE conditions between table1 and table2 (directly or indirectly), although as a "thought experiment" for solving "set algebra" some school children might consider it thus for learning purposes before they have learned more efficient methods.