How to send SQL count data & array data together? - php

Question

I have a script designed to print out values of students who have accrued more than 3 tardies. I want this script to print out both the student name, and the amount of times they've been tardy, but so far I've been only able to print out their names with the following script:
$sql = "select DISTINCT StudentID,classid,date from attendance_main where status = 'Tardy' AND classid like '%ADV%'";
$result = mysql_query($sql) or die (mysql_error());
while($row=mysql_fetch_array($result)) {
$studentid = $row['StudentID'];
$sql2 = "select distinct StudentID,classid,date from attendance_main where StudentID = '$studentid' AND status = 'Tardy' AND classid like '%ADV%'";
$result2 = mysql_query($sql2) or die (mysql_error());
while($row2=mysql_fetch_array($result2)) {
$tardycount = mysql_num_rows($result2);
$studentid = $row2['StudentID'];
if($tardycount >= 3) {
$sql3 = "select * from students where rfid = '$studentid'";
$result3 = mysql_query($sql3) or die (mysql_error());
while($row3=mysql_fetch_array($result3)) {
$fname[] = $row3['fname'];
}
}
}
}
$newdata = array_unique($fname);
foreach ($newdata as $value) {
echo $value;
}
I can't think of how to intuitively do this. Keeping it all in the while loop didn't work (I had multiple results coming up for the same students despite requesting unique entries) so using array_unique was the only method I could think of.
Thanks for any help!

Answer 1

Something like this:
SELECT
attendance_main.StudentID,
students.fname,
COUNT(attendance_main.*) AS `times_tardy`
FROM
attendance_main
INNER JOIN
students
ON
attendance_main.StudentID = students.rfid
WHERE
attendance_main.status = 'Tardy'
AND
attendance_main.classid like '%ADV%'
GROUP BY
attendance_main.StudentID
HAVING
`times_tardy` > 3
Joining the two tables gets you the tardy count and student's name in one query, and the GROUP BY and HAVING clause that get you only the students with more than 3 tardy entries.

Answer 2

You can (and should) do almost everything in SQL. It should look something like this.
select StudentID, classid, date count(*)
from attendance_main
where status = 'Tardy' AND classid like '%ADV%'"
left join student on student.rfid = attendance_main.StudentId
group by StudentId
having count(*) > 3;
Here's how it works.
select the results you want to work with:
select StudentID, classid, date count(*)
from attendance_main
where status = 'Tardy' AND classid like '%ADV%'"
Join the students to your result set on the common id
left join student on student.rfid = attendance_main.StudentId
group everything by student. We use count(*) to get the number of items. We know we're only dealing with tardies because of the where clause in the select.
group by StudentId
limit the results to only tardies above 3 with the having claues (this is like a where clause for the group by)
having count(*) > 3;