Question

I am building a system, mostly for consolidating learning but will be used in practice.

I will try and verbally explain the part of the E-R diagram I am focusing on:

Each cadet can have many uniformID’s

Each Uniform ID is a new entry in table uniform, so cadets (table) may look like:

id | name    | ... | uniformID

1  | Example | ... | 1,2,3

uniform table:

id | notes             | cadet

1  | Need new blahh    | 1

2  | Some stuff needed | 1

3  | Whatever you like | 1

On second thought, looks like I wont need that third column in the db.

I am trying to iterate through each id in uniformID, code:

<?php
$cadet = $_GET['id']; // set  from URL

$query = mysql_query("SELECT `uniformID` FROM `cadets` 
  WHERE id = '$cadet' LIMIT 1") 
  or die(mysql_error()); // get uniform needed as string

// store it
while ($row = mysql_fetch_array($query)) {
  $uniformArray = $row['uniformID']; 
}
echo $uniformArray . "  ";
$exploded = explode(",", $uniformArray); // convert into an array

// for each key in the array perform a new query
foreach ($exploded as $key => $value) {
  $query(count($exploded));
  $query[$key] = mysql_query("SELECT * FROM `uniform` WHERE `id` = '$value'");
}

?>

As I say, this is mainly for consolidation purposes but I have come up with a error, sql is saying:

Fatal error: Function name must be a string in C:\wamp\www\intranet\uniform.php on line 82

line 82 is:

$query[$key] = mysql_query("SELECT * FROM `uniform` WHERE `id` = '$value'");

I wasn’t sure it would work so I tried it and now i’m stuck!

EDIT:

Thanks to everyone who has contributed to this! This is now the working code:

foreach ($exploded as $key => $value) {
              //$query(count($exploded));
              $query = mysql_query("SELECT * FROM `uniform` WHERE `id` = '$value'");
              while ($row = mysql_fetch_array($query)) {
                echo "<tr>
                  <td>" . $row['id'] . "</td>
                  <td>" . $row['note'] . "</td>
                </tr>";
              }
            }

Added the while and did the iteration by nesting it in the foreach

Answer 1

In addition to your tables

cadets(id, ...)
uniforms(id, ...)

use a cross-product table that describes the relation between entities of cadets and entities of uniforms

cadets_x_uniforms(cadet_id, uniform_id)

For each relationship (in this case cadet x has uniform y) put a record with the respective ids into the cross-product table.

… hm, a working example will do better in this case I suppose…

<?php
$pdo = new PDO('mysql:host=localhost;dbname=test;charset=utf8', 'localonly', 'localonly');
$pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$pdo->setAttribute(PDO::ATTR_EMULATE_PREPARES, false);
setup($pdo);

// fetch the uniforms of a specific cadet
$stmt = $pdo->prepare('
    SELECT
        c.name,u.id,u.labelid
    FROM
        so_cadets as c
    LEFT JOIN
        so_cadet_uniform as cxu
    ON
        c.id=cxu.cadet_id
    LEFT JOIN
        so_uniforms as u
    ON
        cxu.uniform_id=u.id
    WHERE
        c.name=?
');
$stmt->execute( array('cadetB') );
$stmt->setFetchMode(PDO::FETCH_ASSOC);
echo "uniforms of cadetB\n";
foreach( $stmt as $row ){
    echo join(', ', $row), "\n";
}

// fetch cadets without uniforms
$query = '
    SELECT
        c.name
    FROM
        so_cadets as c
    WHERE
        NOT EXISTS(SELECT uniform_id FROM so_cadet_uniform as cxu WHERE c.id=cxu.cadet_id)
';
echo "cadets without uniforms\n";
foreach( $pdo->query($query, PDO::FETCH_ASSOC) as $row ){
    echo join(', ', $row), "\n";
}   


function setup($pdo) {
    $pdo->exec('
        CREATE TEMPORARY TABLE so_cadets (
            id int auto_increment,
            name varchar(32),
            primary key(id)
        )
    ');

    $pdo->exec('
        CREATE TEMPORARY TABLE so_uniforms (
            id int auto_increment,
            labelid varchar(32),
            primary key(id),
            unique key(labelid)
        )
    ');

    $pdo->exec('
        CREATE TEMPORARY TABLE so_cadet_uniform (
            cadet_id int,
            uniform_id int,
            primary key(cadet_id,uniform_id)
        )
    ');


    $stmt = $pdo->prepare('INSERT INTO so_cadets (name) VALUES (?)');
    foreach( range('A','F') as $c ) {
        $stmt->execute( array('cadet'.$c));
    }

    $stmt = $pdo->prepare('INSERT INTO so_uniforms (labelid) VALUES (?)');
    foreach( range('K','Z') as $c ) {
        $stmt->execute( array('label'.$c));
    }

    $stmt = $pdo->prepare('INSERT INTO so_cadet_uniform (cadet_id,uniform_id) VALUES (?,?)');
    $cadetHasUniforms = array(
        1=>array(1,2,3), // <- cadetA
        2=>array(7,9), // <- cadetB
        3=>array(8,5,4), // <- cadetC
        // 4=>array() <- cadetD, no entry, no uniforms
        5=>array(10,13,15) // <- cadetE
        // <- cadetE, no entry, no uniforms
    );
    foreach( $cadetHasUniforms as $cadetId=>$uniformIds ) {
        foreach( $uniformIds as $uid ) {
            $stmt->execute(array($cadetId, $uid));
        }
    }

}

prints

uniforms of cadetB
cadetB, 7, labelQ
cadetB, 9, labelS
cadets without uniforms
cadetD
cadetF