FROM and all subsequent JOINs, to be precise. They all generate a single namespace which SELECT uses. As far as I understand the grammar, FROM isn’t even a separate clause, but is itself a separator between a columnset and an expression of the form `t1 JOIN t2 ON cond12 JOIN t3 ON cond123 JOIN …`, where t<n> may be either a table name, or an arbitrarily nested subexpression of the same form.