在查询中使用“ORDER BY count”时出错

Question

I'm using the following query to display some information:

$result = mysqli_query ($con,"SELECT * FROM files,members,member_group WHERE files.member_id = members.member_id AND members.member_id = member_group.member_id AND group_id='$id' ORDER BY count DESC ");

My issue is it works fine when I leave out ORDER BY count DESC but when it is there I get the following error:

Warning: mysqli_fetch_array() expects parameter 1 to be mysqli_result, boolean given in /proj/co600/project/repo/public_html/select_field3.php on line 227

Count is a column in my database which records the number of times a publication is downloaded.

Answer 1

count is an aggregate function, so you need to surround it with backticks.

To get a clear cut picture of your error.. You need to change your code like..

$result = mysqli_query ($con,"SELECT * FROM files,members,member_group WHERE files.member_id = members.member_id AND members.member_id = member_group.member_id AND group_id='$id' ORDER BY count DESC ");
if(!$result)
{
 die(mysqli_error($con));
}