Question

I have a couple tables where there is a same field added. What I want to do is get the earliest year from all these records.

Tables:

comics | movies | tv | tv_episodes

Code So Far (Doesn’t Work):

function getStartYear() {
    include("config.php");
        $query = "SELECT DATE_FORMAT(added, '%Y') as `added` FROM (comics,movies,tv,tv_episodes) ORDER BY `added` DESC LIMIT 1";
        $result = mysql_query($query);
        while ($row = mysql_fetch_array($result)) {
            return $row['added'];
        }
}

Error Returned:

Warning: mysql_fetch_array() expects parameter 1 to be resource, boolean given in E:\xampp\htdocs\mydb\functions\common.php on line 94

What would be the most efficient way to do this?

UPDATE

So going by Andrew’s answer the new query looks like:

function getStartYear() {
    include("config.php");
        $query = "SELECT MIN(y) FROM (
SELECT MIN(YEAR(added)) AS y FROM comics 
UNION SELECT MIN(YEAR(added)) AS y FROM movies 
UNION SELECT MIN(YEAR(added)) AS y FROM tv 
UNION SELECT MIN(YEAR(added)) AS y FROM tv_episodes
) AS t1";
        $result = mysql_query($query);
        if (mysql_num_rows($result) > 0) {
            $finalanswer = mysql_fetch_array($result);
            return $finalanswer['t1']; // <-- Line 96
        }else{
            echo mysql_error();
        }
}

New Message:

Notice: Undefined index: t1 in E:\xampp\htdocs\mydb\functions\common.php on line 96

Answer 1

Could retrieve it through SQL using a UNION sub-query:

SELECT MIN(y) FROM (
    SELECT MIN(YEAR(added)) AS y FROM table1
    UNION SELECT MIN(YEAR(added)) AS y FROM table2
    ...
) AS t1;