Spocitanie (sum) z viacerych tabuliek

<?php
$result = $conn -> query("SELECT SUM(brutto) as brutto, id_middle FROM balik WHERE aktivny_balik = '1' GROUP BY id_middle"); 
        while ($row = $result->fetch_array())
    {
         $brutto = $row['brutto'];
         $id_middle = $row['id_middle'];
    echo 'id - '.$id_middle;
    echo ': metre - '.$brutto;
    echo '<br>';
        
        
    }
?>

$result = $conn -> query
    ("
    SELECT
    id_material,
    SUM(mnozstvo_polozka) - SUM(COALESCE(brutto_sum), 0) AS available_material
FROM
    sklad_polozka
LEFT JOIN (
    SELECT
        SUM(brutto) AS brutto_sum,
        id_middle
    FROM
        balik
    GROUP BY
        id_middle
) AS t
ON sklad_polozka.id = t.id_middle
GROUP BY id_material

    "); 
echo " Error:  - " . $result . "" . mysqli_error($conn);

--
-- Štruktúra tabuľky pre tabuľku `balik`
--

CREATE TABLE `balik` (
  `datum_balik` int(11) NOT NULL,
  `id_balik` mediumint(9) NOT NULL,
  `id_vyrobna_zakazka` int(11) NOT NULL,
  `cislo_balik` tinyint(3) UNSIGNED ZEROFILL NOT NULL,
  `id_zakaznik` int(11) NOT NULL,
  `id_top` int(11) NOT NULL,
  `id_middle` int(11) NOT NULL,
  `id_down` int(11) NOT NULL,
  `brutto` float NOT NULL,
  `chyby` smallint(6) NOT NULL,
  `netto` float NOT NULL,
  `znacka` text CHARACTER SET utf8 COLLATE utf8_bin NOT NULL,
  `info` text CHARACTER SET utf8 COLLATE utf8_bin NOT NULL,
  `id_user` int(11) NOT NULL,
  `aktivny_balik` int(11) NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

--
-- Sťahujem dáta pre tabuľku `balik`
--

INSERT INTO `balik` (`datum_balik`, `id_balik`, `id_vyrobna_zakazka`, `cislo_balik`, `id_zakaznik`, `id_top`, `id_middle`, `id_down`, `brutto`, `chyby`, `netto`, `znacka`, `info`, `id_user`, `aktivny_balik`) VALUES
(1545067388, 1, 6001234, 001, 2, 37, 26, 58, 102, 2, 101.5, '', '', 4, 1),
(1545067399, 2, 6001234, 002, 2, 37, 25, 58, 56, 2, 55.5, '', '', 4, 1),
(1545067410, 3, 6001234, 003, 2, 37, 25, 58, 86, 2, 85.5, '', '', 4, 1);
(1545067555, 6, 6001222, 003, 2, 21, 24, 15, 20, 2, 19.5, '', '', 4, 1);

--
-- Štruktúra tabuľky pre tabuľku `sklad_polozka`
--

CREATE TABLE `sklad_polozka` (
  `id_sklad_polozka` int(11) NOT NULL,
  `id_material` int(11) NOT NULL,
  `id_druh_material` int(11) NOT NULL,
  `datum_sklad_polozka` int(11) DEFAULT NULL,
  `mnozstvo_polozka` int(11) NOT NULL,
  `cena_polozka` float NOT NULL,
  `dodaci_list` varchar(255) NOT NULL,
  `hmotnost` int(11) NOT NULL,
  `cislo_objednavky` varchar(255) DEFAULT NULL,
  `lot_material` varchar(255) NOT NULL,
  `id_user` int(11) NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

--
-- Sťahujem dáta pre tabuľku `sklad_polozka`
--

INSERT INTO `sklad_polozka` (`id_sklad_polozka`, `id_material`, `id_druh_material`, `datum_sklad_polozka`, `mnozstvo_polozka`, `cena_polozka`, `dodaci_list`, `hmotnost`, `cislo_objednavky`, `lot_material`, `id_user`) VALUES
(26, 17, 1, 1545067340, 500, 100, '10121', 100, '5468654', 'U520', 4),
(25, 17, 1, 1545067312, 100, 100, '10121', 10, '47575', 'U100', 4),
(24, 2, 1, 1544435534, 1500, 25, 'nebol', 2000, '7215489', 'U123', 4);

<?php

     $result = $conn -> query
    ("
    SELECT
    id_material, 
    SUM(mnozstvo_polozka) - SUM(COALESCE(brutto_sum, 0)) AS available_material
FROM
    sklad_polozka
LEFT JOIN (
    SELECT
        SUM(brutto) AS brutto_sum,
        id_middle
    FROM
        balik
    GROUP BY
        id_middle
) AS t
ON sklad_polozka.id_sklad_polozka = t.id_middle
GROUP BY id_material
 
    "); 

 while ($row = $result->fetch_array()) 

 {
$result2 = $conn->query("SELECT * FROM sklad_material WHERE id_material = ".$row['id_material']."");
 while ($row2 = $result2->fetch_array()) {
     echo $row2['nazov_material'];
 }
echo ' - ';
echo $row['available_material'];
echo '<br>';
 }    
?>