Extracting member's first name from member table using results from another table

<?php
include 'dbFunctions.php';
$courseid = $_GET['Course_id'];

$query = "SELECT * FROM course WHERE Course_id=".$courseid."";
$arrCourse = executeSelectQuery($query);

$qu开发者_如何学Goery2 = "SELECT * FROM course_member WHERE Course_id=".$courseid."";

$result = mysqli_query($link,$query2) or die(mysqli_error($link));
?>

HTML body:

<?php
while ($row = mysqli_fetch_array($result)) {
?>

      <?php echo $row['member_id']
      ?>

      <?php
}
?>

this correctly prints the results of the member id that is involved in the selected course, however, i want to extract the first_name using the result generated that belong to another table called member.

been trying all the join queries but it didn't work.

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Sounds like you need to read up on the JOIN operation in SQL. The following query will return all the data you seem to need, from a single query:

SELECT * 
FROM course
INNER JOIN course_member ON course.id = course_member.course_id
INNER JOIN member ON member.id = course_member.member_id

---

As far as I see

$sql="select last_name from course_member 
join member on course_member.member_id = member.member_id
where course_member.Course_id = ".$courseid;

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I'm going to take a guess here at your table defs...

$query2 = "SELECT m.first_name, cm.* FROM course_member cm join member m on m.id = cm.member_id WHERE Course_id=".$courseid."";

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If you want only the member name and you are not much interested with the id then you can merge it into a single query

 $query = SELECT fName from member WHERE id = (SELECT member_id FROM course_member WHERE Course_id=$courseid);