如何在PHP / MySQL中显示选定的列

Question

I am running this query in PHP:

$sql="SELECT t.* FROM tickets t join 
(select ticketnumber, max(datetime) as maxdt from ticket_updates tu GROUP BY ticketnumber) tu

ON t.ticketnumber = tu.ticketnumber

WHERE t.status <> 'Completed' AND tu.maxdt < now() - interval 1 hour; ";
$rs=mysql_query($sql,$conn);
while($result=mysql_fetch_array($rs)) {
    echo $result["tu.maxdt"];
}

but its not showing the datetime column

what am i doing wrong?

Answer 1

you are selecting max(datetime) as maxdt in a sub select. This won't come out as tu.maxtd and it needs to be included in the main select

SELECT t.*, max(tu.datetime) as maxdt FROM tickets

echo $result["maxdt"];

As an aside mysql_ functions are deprecated, you should switch to mysqli_ . https://wiki.php.net/rfc/mysql_deprecation

Answer 2

You've got to include this column in your query:

$sql="SELECT t.*, tu.* FROM tickets t join 
(select ticketnumber, max(datetime) as maxdt from ticket_updates tu GROUP BY ticketnumber) tu

ON t.ticketnumber = tu.ticketnumber

WHERE t.status <> 'Completed' AND tu.maxdt < now() - interval 1 hour; ";

Answer 3

The column is called maxdt not tu.maxdt so it needs to be echo $result['maxdt'] . You also need to include the column in your select statement:

SELECT t.*, tu.* 
FROM tickets t join 
(SELECT ticketnumber, max(datetime) AS maxdt 
 FROM ticket_updates tu 
 GROUP BY ticketnumber) tu 
...