Question

so I have a query like this:

(SELECT last_updated FROM ...) UNION (SELECT last_updated FROM ...) ORDER BY last_updated

Notice that the ORDER BY statement is outside both parentheses…When I run the query it appears that it does a combined order by last_updated (which is what I want to do). IE. it took the combined unioned result set and order them all by last_updated as a single set.

However, I want to confirm that this is indeed what this will do, so does anyone have any link to some docs that confirm that this will indeed happen? Can anyone confirm for a FACT that this will indeed happen if you perform the query this way?

Answer 1

From UNION Syntax:

To apply ORDER BY or LIMIT to an individual SELECT, place the clause inside the parentheses that enclose the SELECT

and a paragraph later:

To use an ORDER BY or LIMIT clause to sort or limit the entire UNION result, parenthesize the individual SELECT statements and place the ORDER BY or LIMIT after the last one.