mysql - How to use mysql_fetch_assoc to process records in php? -

i trying retrieve subject names, there 2 types of subjects optional , main. each student contains optional , main subjects. using subject ids can retrieve name subject table. in result 1 optional subject name appearing, there problem in code? pls me

  $subject_names = array(); for($i=0;$i<count($student_num_data);$i++) {     $optional_id_list = mysql_query("select optional_subject_id ms_student student_id = ".$student_num_data[$i]['student_id']);     while($row = mysql_fetch_assoc($optional_id_list))     {         foreach ($row $key)          {             $optional_subject = mysql_query("select subject_name ms_subject subject_id = ".$key['optional_subject_id']);              $optional_subject_name = array();             while($row1 = mysql_fetch_assoc($optional_subject))             {                 $optional_subject_name[] = $row1;               }         }     }     $subject_id_list = mysql_query("select subject_ids subject_config stream_index =".$stu_stream);       while($row = mysql_fetch_assoc($subject_id_list))     {         foreach ($row $key)          {             $main_subject = mysql_query("select subject_name ms_subject subject_id = ".$key['subject_ids']);              $main_subject_name = array();             while($row3 = mysql_fetch_assoc($main_subject))             {                 $main_subject_name[] = $row3;               }         }     }      $subject_names = $main_subject_name[0]['subject_name'].','.$optional_subject_name[0]['subject_name'];      $small_subject_name=trim($subject_names);//remove whitespace @ end of string              $small_subject_name = str_replace(" ", "-", $small_subject_name); // replaces spaces hyphens.          $small_subject_name = preg_replace('/[^a-za-z0-9\-]/', '', $small_subject_name); // removes special chars.          $small_subject_name =  preg_replace('/-+/', '-', $small_subject_name); // removes multiple hyphens.                 $small_subject_name = str_replace("-", " ", $small_subject_name); // replaces hyphens spaces.                 $small_subject_name=strtolower(str_replace(" ","_",$small_subject_name));        if($stu_class == 11 || $stu_class == 12)     {           $subject_statement = $subject_statement."if(".$small_subject_name."='ab','ab',round(".$small_subject_name.",2)) ".$small_subject_name.",";            $sum_subject_statement = $sum_subject_statement.'ifnull(`'.$small_subject_name.'`,0) + ';                    /* start 1022 02-09-2014 */         $subject_pass_statement .= $small_subject_name." >= 33 , ";                $subject_pass_statement = substr($subject_pass_statement,0,strlen($subject_pass_statement)-5);         $update_pass_statement = "update ".$table_name." set class_rank = 'p' 1=1 ".$track_div_stmnt.$id_stmnt." , student_id = ".$student_num_data[$i]['student_id']." , ".$subject_pass_statement;         $update_pass_query=mysql_query($update_pass_statement);     } } 

this not mysql_fetch_assoc function, logic of code. having hard time, because of how code looks. facing many problems @ once, reasonable solution here to:

decompose problem

1. think main tasks / actions code do.
   let's say:
   1. for every student, retrieve optional subjects enrolled.
   2. then retrieve main subjects taking.
   3. and retrieve results determine subjects have passed , did not.

2. start code expresses intetion, use functions don't exist yet:

    $passstatementforyear = new passstatement($year);  $students = getstudentsforschoolyear($year);  foreach ($students $student) {      $optionalsubjects = loadoptionalsubjectsforstudent($student);      $mainsubjects = loadmainsubjectsforstudent($student);      $passreport = preparereportforstudent(          $student, $optionalsubjects, $mainsubjects      );      updatepassstatementusingstudentsreport(          $passstatementforyear, $passreport      );  } 

3. build missing parts (functions, classes etc.)

now need take care of standalone steps. every function introduces new small problem, can take care of in isolate , simple manner. then, if find having issues mysql_fetch_assoc, refer official documentation , example show:

$sql = "select id userid, fullname, userstatus           sometable          userstatus = 1";  $result = mysql_query($sql);  if (!$result) {     echo "could not run query ($sql) db: " . mysql_error();     exit; }  if (mysql_num_rows($result) == 0) {     echo "no rows found, nothing print exiting";     exit; }  // while row of data exists, put row in $row associative array // note: if you're expecting 1 row, no need use loop while ($row = mysql_fetch_assoc($result)) {     echo $row["userid"];     echo $row["fullname"];     echo $row["userstatus"]; }  mysql_free_result($result);