SQL call keeps on returning error - php

Question

The SQL call below keeps returning:
Fatal error: Call to a member function fetch_assoc() on a non-object in /home/content/76/10930776/html/apprentice/report.php on line 86
$sql = "select sum(".$column.") as totalmeetings,username from data where datediff(max(dateinput),min(dateinput)) <= ".$daysdifference." group by username ";
echo $sql;
$result = $mysqli->query($sql);
while($pcresult = $result->fetch_assoc())//line 86
{
}
What am i doing wrong?
The SQL call prints out like this:
select sum(prospects1stmeeting) as totalmeetings,username from data where datediff(max(dateinput),min(dateinput)) <= 500 group by username

Answer 1

try this query
select sum(prospects1stmeeting) as totalmeetings,username from data
group by username
having datediff(max(dateinput),min(dateinput)) <= 500

Answer 2

Look at how you're trying to access the results:
$result = $mysqli->query($sql);
while($pcresult = $result_percentile->fetch_assoc())//line 86
{
}
$result and $results_percentile are not the same thing. You should try:
$result = $mysqli->query($sql);
while($pcresult = $result->fetch_assoc())//line 86
{
}
unless you're not showing your whole code.
EDIT
But since you edited your question to no longer reflect this answer, the answer is still that you're trying to access a non object. That means $result does not produce data that can be read as an associative array.