有两个表要一起工作。
第一个表:
AttendanceID TeacherID BatchID SubjectID SemesterID Date
32 110 8 9 1 2016-08-04
31 102 8 10 1 2016-07-17
30 108 6 22 3 2016-06-27
29 109 7 18 2 2016-06-27
28 109 8 13 1 2016-06-27
27 110 7 7 2 2016-06-27
26 110 8 9 1 2016-06-27
25 104 2 42 7 2016-04-20
24 104 5 35 5 2016-04-14
23 104 2 42 7 2016-04-14
22 102 2 41 7 2016-04-13
21 102 2 41 7 2016-04-10
20 102 6 23 3 2016-04-10
19 102 6 23 3 2016-04-10
第二张表:
第一个表由唯一的行组成,这些行将用于表二中的每个新出席列表。
例如:在第一个表中,AttendanceID
21
在第二个表中用于特定主题的完整出勤。
我想计算特定Subject
的第二个表中所有学生的百分比,总数可以通过第一个表AttendanceID
我在 PHP 中所做的是:首先,我使用此查询从第一个表中获取总数:
SELECT COUNT(AttendanceID) FROM attendances WHERE SubjectID = ? AND BatchID = ?"
一旦我从第一个表中获得特定主题和批处理的总出席人数,我将其存储在变量 $total
中,然后我编写另一个查询以从第二个表中获取获得的出席人数:
SELECT COUNT(AttendanceDetailID) FROM attendancedetail WHERE CollegeID = ? AND Status = 'present' AND SubjectID = ?"
获得出勤率后,我将其存储在变量 $obtained
中
一旦我获得了这两个值,我就会像这样计算 PHP 中的百分比:
if(!empty($total) && !empty($obtained)) {
$result = (($obtained * 100)/ $total);
$result = round($result);
}
完整的PHP代码如下:
public function showStateOfAttendance($subjectID, $batchID){
$st = $this->conn->prepare("SELECT CollegeID, Name, Gender, Photo FROM students WHERE BatchID = ?");
$st->bind_param("i", $batchID);
$st->execute();
$st->store_result();
$num_rows = $st->num_rows;
$st->bind_result($college_id, $name, $gender, $photo);
$this->response['attendance'] = array();
while($st->fetch()) {
$this->calcultaionOfAttendance($subjectID, $college_id, $name, $gender, $photo, $batchID);
}
return json_encode($this->response);
$st->free_result();
$st->close();
}
public function calcultaionOfAttendance($subjectID, $studentID, $name, $gender, $photo, $batchID) {
$stmt = $this->conn->prepare("SELECT COUNT(AttendanceID) FROM attendances WHERE SubjectID = ? AND BatchID = ?");
$stmt->bind_param("ii", $subjectID, $batchID);
$stmt->execute();
$stmt->store_result();
$num_rows = $stmt->num_rows;
$stmt->bind_result($AttendanceID);
while($stmt->fetch()) {
$total = $AttendanceID;
}
$stmt->free_result();
$stmt->close();
$stmt2 = $this->conn->prepare("SELECT COUNT(AttendanceDetailID) FROM attendancedetail WHERE CollegeID = ? AND Status = 'present' AND SubjectID = ?");
$stmt2->bind_param("ii", $studentID, $subjectID);
$stmt2->execute();
$stmt2->store_result();
$stmt2->bind_result($AttendanceDetailID);
while($stmt2->fetch()){
$obtained = $AttendanceDetailID;
}
if(!empty($total) && !empty($obtained)) {
$result = (($obtained * 100)/ $total);
$result = round($result);
$rating = ($result)/20;
$tmp = array();
$tmp['result'] = $result;
$tmp['total'] = $total;
$tmp['obtained'] = $obtained;
$tmp['rating'] = $rating;
$tmp['name'] = $name;
$tmp['college_id'] = $studentID;
$tmp['gender'] = $gender;
$tmp['photo'] = $photo;
array_push($this->response['attendance'],$tmp);
//var_dump(array($total, $obtained, $result, $rating, $studentID, $name));
}else if(empty($total)) {
$tmp = array();
$tmp['result'] = 0.0;
$tmp['total'] = 0.0;
$tmp['obtained'] = $obtained;
$tmp['rating'] = 0.0;
$tmp['name'] = $name;
$tmp['college_id'] = $studentID;
array_push($this->response['attendance'],$tmp);
//var_dump(array("0.0",$obtained, "0.0","0.0",$studentID,$name));
}else if(empty($obtained)) {
$tmp = array();
$tmp['result'] = 0.0;
$tmp['total'] = $total;
$tmp['obtained'] = 0.0;
$tmp['rating'] = 0.0;
$tmp['name'] = $name;
$tmp['college_id'] = $studentID;
array_push($this->response['attendance'],$tmp);
//var_dump(array($total, "0.0", "0.0","0.0", $studentID , $name));
}
}
这是我所做的查询的 android 屏幕截图:以下结果是针对 SubjectID = 23
和 BatchID = 6
它为我提供了所需的结果,但我需要更好的方法来计算它,是否可以通过单个查询来实现?
谢谢
最佳答案
尝试:
SELECT s.CollectID, s.Name, s.Gender, s.Photo,
(SELECT count(AttendanceID) from attendances WHERE SubjectID =? and BatchID = s.BatchID) as total,
(SELECT count(AttendanceDetailID) FROM attendancedetail WHERE CollegeID = s.CollectID and Status = 'present' and SubjectID = ?) as obtained
FROM students s
WHERE s.BatchID = ?
关于php - 如何计算所有在场学生的百分比,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/38802447/