MYSQL Count Method - php

Question

function sum($nomId){
$sql = "SELECT SUM(nomDetCantidad) FROM table2 where Id = $nomId";
$Resultado=$this->ProcesaSQLQueryList($sql);
if($Resultado>0){
foreach($Resultado as $key => $valor){
$cantidadTotal = $valor[0];
}
}
if($Resultado=='null'){$cantidadTotal=0;}
$sql = "UPDATE table1 SET nomCantidadTotal=$cantidadTotal,nomActualizado = NOW() WHERE nomId= $nomId";
return $this->ProcesaSQLQueryUpdate($sql);
and this is the function I call
function ProcesaSQLQueryList($SQLQuery){
$row= array();
if(!$this->link_mysql) $this->link_mysql = conectarManager();
if($res = mysql_query($SQLQuery,$this->link_mysql)){
while($r = mysql_fetch_array($res)){
$row[] = $r;
}
mysql_free_result($res);
return $row;
}else{
$this->last_error = $SQLQuery . " - " . mysql_error();
return -1;
}
}
So I sum up whatever I have in a field table 2 with the foreign key of table 1 then my result gets updated to the table 1 field but if I delete the fields in table 2 result wont get updated to 0 any suggestions I'm pretty sure this is an easy one but can't seem to find it

Answer 1

$sql = "SELECT SUM(nomDetCantidad) FROM table2 where nominaId = $nomId";
$Resultado = $this->ProcesaSQLQueryList($sql);
if ($Resultado > 0) {
foreach ($Resultado as $key => $valor) {
$cantidadTotal = $valor[0];
}
}
if ($cantidadTotal == '') {
$cantidadTotal=0.00;
}
$sql = "UPDATE table1 SET nomCantidadTotal=$cantidadTotal,nomActualizado = NOW() WHERE nomId = $nomId";
return $this->ProcesaSQLQueryUpdate($sql);
There! It was sending me a blank variable xD but fixed and there are more suitable ways to do it, I agree with Spencer but if a client wants a red swing he has to get a red swing you know? :) thanks for the help guys!

Answer 2

If you need a zero returned when there are no "matching" rows in table2, then wrap the return expression in an IFNULL function.
SELECT IFNULL(SUM(nomDetCantidad),0) FROM table2 ...
You could significantly reduce the amount of code you have, reduce the number of roundtrips to the database, and improve performance by doing all this work in a single UPDATE statement. You can use either a correlated subquery or an OUTER JOIN:
-- using a correleated subquery
UPDATE table t1
SET t1.nomActualizado = NOW()
, t1.nomCantidadTotal =
( SELECT IFNULL(SUM(t2.nomDetCantidad),0) AS nomCantidadTotal
FROM table2 t2
WHERE t2.Id = t1.nomID
)
WHERE t1.nomId = $nomId
-- using an OUTER JOIN
UPDATE table1 t1
LEFT
JOIN (SELECT t2.Id, SUM(t2.nomDetCantidad) AS nomCantidadTotal
FROM table2 t2
WHERE t2.Id = $nomId
GROUP BY t2.Id
) s
ON s.Id = t1.nomID
SET t1.nomCantidadTotal = IFNULL(s.nomCantidadTotal,0)
, t1.nomActualizado = NOW()
WHERE t1.nomID = $nomId
It's not at all clear why you need to store this total on table1, when you could derive it from table2 whenever you need it, without storing that value on table1 at all...
SELECT t1.nomId
, IFNULL((SELECT SUM(t2.nomDetCantidad) AS nomCantidadTotal
FROM table2 t2
WHERE t2.Id = t1.nomID
),0) AS nomCantidadTotal
FROM table1 t1
WHERE t1.nomId = $nomId