Question

I currently have a database with 12 tables. I am doing a php query to pull the information from the database but I am not getting anything displayed. The query alone bridges all the tables starting with table schedule that have a foreign key related. Should I need to start the query from the table class and bridge with other tables?

TABLE DESIGN- PICTURE

If you like to duplicate my design- QUERY

$query = ("SELECT  class_name, class_caption, class_credit_hours, class_description
                FROM schedule 
                INNER JOIN section 
                ON class.id = section.class_id
                INNER JOIN faculty
                ON faculty.id = section.faculty_id
                INNER JOIN faculty
                ON faculty.id = office_hours.faculty_id
                INNER JOIN faculty_titles
                ON faculty_titles.faculty_id = faculty.id
                INNER JOIN faculty_education
                ON faculty_education.faculty_id = faculty.id 
                INNER JOIN section
                ON section.faculty_id = faculty.id 
                INNER JOIN class
                ON class.id = section.class_id
                INNER JOIN major_class_br
                ON major_class_br.class_id = class.id
                INNER JOIN  major_minor 
                ON major_class_br.major_minor_id = major_minor.id                
                 ");
      //execute query
      $result = mysql_query($query);

     if ($result){

    $totalhours = 0;

    while ($row = mysql_fetch_assoc( $result ))
    {  
        print "<b>" . $row['class_name'] . "</b><br>";
        print $row['class_caption'] . "<br>";
        print $row['class_description'] . "<br>";
        print $row ['class_credit_hours'] . "hrs. <br>";
        print "------------------------------<br />";
        $totalhours += $row['class_credit_hours']; 
    }   
    }

SQL fiddle query

Answer 1

SELECT  class_name, class_caption, class_credit_hours, class_description
             FROM schedule 
            INNER JOIN section 
            ON class.id = section.class_id

Right here there’s a problem: you are doing a INNER JOIN using the field ‘class.id’ but the table ‘class’ isn’t in either side of the JOIN. So it won’t work.

The query should start like this:

SELECT  class_name, class_caption, class_credit_hours, class_description
             FROM class
            INNER JOIN section 
            ON class.id = section.class_id

And then do the JOIN with the table ‘schedule’ with the table it shares a common index (I guess it would be class).

The complete query should be something like this:

SELECT  class.class_name, class.class_caption, class.class_credit_hours, class.class_description
            FROM class
            INNER JOIN section 
            ON class.id = section.class_id
            INNER JOIN faculty 
            ON faculty.id = section.faculty_id OR faculty.id = office_hours.faculty_id
            INNER JOIN faculty_titles
            ON faculty_titles.faculty_id = faculty.id
            INNER JOIN faculty_education
            ON faculty_education.faculty_id = faculty.id 
            INNER JOIN major_class_br
            ON major_class_br.class_id = class.id
            INNER JOIN major_minor 
            ON major_class_br.major_minor_id = major_minor.id
            INNER JOIN sched_sect_br 
            ON sched_sect_br.section_id =  section.id
            INNER JOIN schedule
            ON schedule.id = sched_sect_br.schedule_id
            INNER JOIN semester
            ON semester.id = schedule.semester_id
            INNER JOIN office_hours
            ON schedule.id = office_hours.schedule_id AND faculty.id = office_hours.faculty_id

This query gets info from all the tables you have in your graph, aside from the event table, that isn’t related to any other. But still this query should have more fields on the SELECT (you are only selection fields from the class table, I understand you’d want data from the other 10 tables as well), to do this simple add ‘tablename.field’ to the list of fields from the SELECT.