如何在Twig HTML表中显示来自递归SQL查询的分组数据？

Question

I want to be able to display data from a SQL database (using PDO) and present it in an HTML table, however, I am having trouble understanding how to include a subquery in the results of my original query. I have gotten close to my desired result by using the GROUP_CONCAT function to group the data as comma separated values.

Using Twig to populate the HTML table with the desired values, but I can't figure out how to group certain values (course names) underneath the student.

`PHP
SELECT classes.ID, classes.PIDM, classes.fName, classes.lName, classes.advisorOneFirst, classes.advisorOneLast, classes.advisorOneEmail, 
GROUP_CONCAT(classes.courseTitle) AS courses
FROM classes
WHERE term = :cterm AND (classes.MGrade = "F" OR classes.MGrade = "F~" OR classes.MGrade = "D" OR classes.MGrade = "D~")
GROUP BY classes.ID
ORDER BY lName ASC

`HTML
{% for student in classes %}
<tr>
<td>{{student.fName}}</td>
<td>{{student.courses}}</td>
</tr>
{% endfor %}

To illustrate my webpage looks like this:

student1 course1,course2
student2 course3,course4

And I want it to look like this:

student1 course1
         course2
student2 course3
         course4

Also, using

GROUP_CONCAT(classes.courseTitle SEPARATOR "<br>")

or any other substitution results in:

student1 course1<br>course2
student2 course3<br>course4

Answer 1

Twig automatically escapes your variables to protect against XSS attacks, which is why using the <br> tags wasn't working. Using the GROUP_CONCAT(classes.courseTitle SEPARATOR "<br>") , update your twig to use the raw filter:

{% for student in classes %}
<tr>
<td>{{student.fName}}</td>
<td>{{student.courses|raw}}</td>
</tr>
{% endfor %}

---

Update

Using the raw filter could produce other issues depending on the characters in courses. A better approach would be to use a character you can split on as the separator in group_concat , then split on that character and loop each course in twig. For example, if you used a semicolon as the character separator,

Your group concat would look like this:

GROUP_CONCAT(classes.courseTitle SEPARATOR ';')

And your twig would like this:

{% for student in classes %}
<tr>
    <td>{{ student.fName }}</td>
    <td>
    {% for course in student.courses|split(';') %}
        {{ course }}<br>
    {% endfor %}
    </td>
</tr>
{% endfor %}

Answer 2

given a generalized table:

 myTable
=========
foo | bar
----+----
foo1|bar1
foo2|bar2
foo1|bar3
foo2|bar4

SQL

SELECT foo,
GROUP_CONCAT(bar SEPARATOR "@@@") AS bars
FROM myTable
GROUP BY foo

HTML

{% for foobar in myTable %}
<tr>
    <td>{{foobar.foo}}</td>
    <td>
    {% for bar in foobar.bars|split("@@@") %}
    {{bar}}<br>
    {% endfor %}
    </td>
</tr>
{% endfor %}

webpage presentation

foo1 bar1
     bar3
foo2 bar2
     bar4