Question

I have a relational database with one main table linked to other tables with foreign keys. I am trying to write a reporting tool in PHP to grab all the data out but have gotten stck with one part of it.

here is my query so far:

SELECT * 
FROM student s 
LEFT OUTER JOIN ep e ON s.sID = e.sID 
LEFT OUTER JOIN ntc n ON s.sID = n.sID 
LEFT OUTER JOIN pk p ON s.sID = p.sID 
LEFT OUTER JOIN roa r ON s.sID = r.sID 
WHERE s.sID = '$id'

ep, ntc and pk are all 1:1 with student so there are no problems. But the roa table holds multiple records (spanning multiple rows) for each student.

roa table structure:

+----------+--------------+------+-----+-------------------+----------------+
| Field    | Type         | Null | Key | Default           | Extra          |
+----------+--------------+------+-----+-------------------+----------------+
| roaID    | int(11)      | NO   | PRI | NULL              | auto_increment |
| sID      | int(11)      | NO   | MUL | NULL              |                |
| roa      | varchar(255) | NO   |     | NULL              |                |
| roaStaff | varchar(50)  | NO   |     | NULL              |                |
| visible  | tinyint(1)   | NO   |     | 1                 |                |
+----------+--------------+------+-----+-------------------+----------------+

where a select * from roa where sID = 1 returns:

+-------+-----+---------------+----------+---------+
| roaID | sID | roa           | roaStaff | visible |
+-------+-----+---------------+----------+---------+
|    41 | 1   | Description 1 | Staff 1  |       1 |
|    60 | 1   | Description 2 | Staff 2  |       1 |
+-------+-----+---------------+----------+---------+

what I am after my original query to achieve is a result something like:

<-student, etc data
..-------+-----+-----------------------------------------------+---------+
.. roaID | sID | roa                                           | visible |
..-------+-----+-----------------------------------------------+---------+
..    41 | 1   | Description 1 Staff 1, Description 2 Staff 2  |       1 |
...
...

so that both the roa.roa and the roa.roaStaff are all in one cell.

I have tried using GROUP_CONCAT but have only been able to get it to work for one column, not group multiple columns together.

any help is greatly appreciated.

regards.

Answer 1

try something like this,

SELECT ......, GROUP_CONCAT(CONCAT(roa, ' ', roaStaff)) roa
FROM ...

so when you plug it in your query,

SELECT * 
FROM student s 
LEFT OUTER JOIN ep e ON s.sID = e.sID 
LEFT OUTER JOIN ntc n ON s.sID = n.sID 
LEFT OUTER JOIN pk p ON s.sID = p.sID 
LEFT OUTER JOIN 
(
    SELECT sID, GROUP_CONCAT(CONCAT(roa, ' ', roaStaff)) roa
    FROM roa 
    GROUP BY sID
) r ON s.sID = r.sID 
WHERE s.sID = '$id'

follow-up question, how about the visible field on table roa? How would you want it to be shown

SIDENOTE

your query is vulnerable with SQL INJECTION, please read the article below to learn how to protect from it

• How can I prevent SQL injection in PHP?