Question

I have 3 tables: questions, articles and pictures

The rows in each table contain a current_timestamp column posted, and link to an id. I’d like to sort the results of the rows of all three by their timestamp and only echo the newest of the three (for example: if the question is newest from the ID, display that only)

if(count($interests) != 0){ foreach($interests as $interests_following){
    $interestid = mysql_result(mysql_query("SELECT `id` FROM `interests` WHERE `name` = '$interests_following'"),0);
    $interestquestions = @mysql_result(mysql_query("SELECT `question_text`, `posted` FROM `questions` WHERE `interest` = '$interests_following'"),0);
    $interestarticles = @mysql_result(mysql_query("SELECT `article_title`, `posted` FROM `articles` WHERE `interest_id` = '$interestid'"),0);
    $interestpictures = @mysql_result(mysql_query("SELECT `interest_pic_title`, `posted` FROM `interest_pictures` WHERE `interest_id` = '$interestid'"),0);

echo '.$interests_following.': //<Only display 1 newest item (article/picture/question here>

Answer 1

Use UNION ALL:

SELECT posted 
FROM
(
    SELECT `question_text`, `posted` FROM `questions` 
    WHERE `interest` = '$interests_following'
    UNION ALL
    SELECT `article_title`, `posted` FROM `articles` 
    WHERE `interest_id` = '$interestid'
    UNION ALL
    SELECT `interest_pic_title`, `posted` FROM `interest_pictures` 
    WHERE `interest_id` = '$interestid'
) t
ORDER BY posted DESC LIMIT 1