Mysqli在查询中是否支持MAX？

Question

I want to get the last date from a table. So I can show the last added or changed item:

$qry = " 
        Select
            MAX(changedate)
        FROM
            producten   
        ";
    $stmt = $connection->prepare($qry);             
    $stmt->error;
    $stmt->execute();
    $result = $stmt->get_result();
    $up = $result->fetch_assoc();
    $stmt->close();

$main .='Last update '.$up['changedate'];

But I receive this error message:

Notice: Undefined index: changedate in /home/jcslnl/domains/jcsl.nl/public_html/michael/paginas/home.php on line 22

Is this because MAX is not longer supported? Or should I continue to search for the error?

It could also be that I did something wrong in the table, it's the firsttime i used timestamp i.s.o. unix timestamp.

Answer 1

The answer to your question is yes, mysqli supports MAX. However, you need to alias the column, since you aren't actually selecting the column changedate, but the result of a function which selects the value of changedate. In which case SELECT MAX(changedate) as changedate provides you with the desired result.

You can also use var_dump($up); to see this more clearly in your result.