加入两个while循环以根据日期顺序显示

Question

So I have this MySQL query which is basically just two single while loops running and displaying info as they should, the issue with this is they display information like:

Test1, Test2, Test1, Test2, Test1, Test2, Test3, Test4, Test3, Test4, etc...

As you would expect. Although what I am looking to do is arrange these results based on the dates they were added to the table, so if one set of test 3 and test 4 were added most recently, it would show as:

test3, test4, test1, test2, test1, test2, test3, test4 etc...

So kind of rearranging these results based on the dates? I know using ORDER BY would only show each section in order but is there a way using my code which I can mix them ALL up and rearrange by both date_added and date_earned?

$user_id = $_SESSION['userid'];                 
$sql8 = "SELECT * FROM table1 ORDER BY date_added;";

if ($result8 = $conn->query($sql8)) {

    /* fetch associative array */
    while ($row8 = $result8->fetch_assoc()) {
        printf ("%s (%s)
", $row8["test1"], $row8["test2"]);
    }
}

$user_id = $_SESSION['userid'];                 
$sql9 = "SELECT * FROM table2 ORDER BY date_earned";

if ($result9 = $conn->query($sql9)) {

    /* fetch associative array */
    while ($row9 = $result9->fetch_assoc()) {
        printf ("%s (%s)
", $row9["test3"], $row9["test4"]);
    }
}    

Answer 1

use union all

Select * from(
SELECT * FROM table1 
union all
SELECT * FROM table2 
) tab ORDER BY date_added,date_earned