PHP and SQLite - Multiply Certain Column Values Together - php

Question

I'm retrieving some data from a database where the values might be something like the following:
Column1 | Column2
-----------------
Bob | 24
Joe | 17
Jimmy | 38
Joe | 10
Bob | 5
Sam | 8
With this data, I want to somehow select the Bob rows and multiply them together. I want to do this for all rows that match in Column1. I'm not concerned about doing it in SQLite, but what is the best way to go about this in PHP? I've currently added the results to an array in PHP by doing the following:
$myArray[$resultRow['Column1']] = $resultRow['Column2'];
I was wondering how to go about navigating through this and finding matching keys, multipying their values together, and outputting something like
Column1 = Column2-a * Column2-b

Answer 1

consider this code:
$results = array();
foreach(array('Bob' => 24, 'Joe' => 17, 'Jimmy' => 38, 'Joe' => 10, 'Bob' => 5, 'Sam' => 8) as $key => $val){
$results[$key][] = $val;
}
echo '<pre>';
print_r($results);
echo '</pre>';
out put:
Array
(
[Bob] => Array
(
[0] => 5
)
[Joe] => Array
(
[0] => 10
)
[Jimmy] => Array
(
[0] => 38
)
[Sam] => Array
(
[0] => 8
)
)
PHP ignores duplicate key, you have to create $results array when you retreiving the data from database, lets assume that you do like this:
while () {
$col1 = $row["col1"];
$col2 = $row["col2"];
$results[$col1][] = $row["col2"];
}
now the results array must be like this:
Array
(
[Bob] => Array
(
[0] => 24
[1] => 5
)
[Joe] => Array
(
[0] => 17
[1] => 10
)
[Jimmy] => Array
(
[0] => 38
)
[Sam] => Array
(
[0] => 8
)
)
now, its easy to search for colmun1 names like this:
$values_for_colmn1 = $results[$column1]; //which is an array
// use array_product() function for array product
$product_for_column1 = array_product($values_for_colmn1);

Answer 2

First, to read only Bob's values:
$stmt = $db->prepare('SELECT Column2 FROM MyTable WHERE Column1 = ?')
$stmt->bindValue(1, 'Bob', SQLITE3_TEXT);
$result = $stmt->execute();
Then, multiply all of them:
$value = 1.0;
while ($res = $result->fetchArray()) {
$value = $value * $res['Column2'];
}