That's not the row syntax though, that's the sub-select syntax (my initial confusion). i.e., there are three options according to the grammar: SET { column_

That's not the row syntax though, that's the sub-select syntax (my initial confusion). i.e., there are three options according to the grammar: SET { column_name = { expression | DEFAULT } | ( column_name [, ...] ) = [ ROW ] ( { expression | DEFAULT } [, ...] ) | ( column_name [, ...] ) = ( sub-SELECT ) } The second option, "row" syntax (to which the optional "ROW" keyword was recently added), doesn't allow for a row expression, only column expressions. The sub-select syntax suffices for row expressions (as your example demonstrates).