พี่ครับ วานรบกวนช่วยดูข้อมูล SQL ผม กับ ตารางและโจทย์ของผมให้ที่ครับ กำลัง งง

<?php
	$con=mysqli_connect("localhost","root","","ae2de");
	mysql_query("SET NAMES UTF8");

	if(mysqli_connect_errno($con))
	{
		echo "ไม่สามารถเชื่อมต่อได้" . mysqli_connect_errno();
	}
	//$result = mysqli_query($con,"SELECT * FROM work") ;
	
																


$result = mysqli_query($con,"SELECT work.work_id,topic,detail,student.name as student  FROM assing , work , student  where `work`.`work_id` = `assing`.`student_id` AND `student`.`student_id` AND `student`.`student_id`='1'");
$arr=array();
while($row = mysqli_fetch_array($result))
{

	$arr[]=$row;
}



	
	echo json_encode($arr);
	mysqli_close($con);
?>

<?php

$con=mysqli_connect("localhost","root","","ae2de");

// Check connection
if (mysqli_connect_errno($con))
{
  echo "Failed to connect to MySQL: " . 	mysqli_connect_error();
}


//$result = mysqli_query($con,"SELECT * FROM work where work_id=$work_id");
//$result = mysqli_query($con,"SELECT *  FROM teacher , work where work.work_id = teacher.teacher_id");
$result=mysqli_query($con,"SELECT *  FROM assing , work ,student where `work`.`work_id` = `student`.`student_id` AND `assing`.`student_id` = `student`.`student_id`");


$arr=array();

$row = mysqli_fetch_object($result);
$arr[] = $row;

//$str .= "<li><h1>name:" . $row['topic'] . " password:" . $row['detail'] . "</h1></li>";  	

echo json_encode($arr);

mysqli_close($con);
?>

SELECT topic,student.name as student,teacher.name as teacher FROM assing , work , student , teacher where work.work_id = assing.work_id and assing.student_id=student.student_id and teacher.teacher_id = assing.teacher_id and weekNumber = 2 and student.student_id = 2