按其他列分组时列的总和

Question

So this is the structure of my MySQL table that I wanna work this out with:

 ID type     category_id amount
 12 Expense     3        963.39
 13 Expense     5        1200.50
 14 Expense     3        444.12
 15 Expense     5        1137.56
  ..............................

Desired output:

 1407,41 (for category_id = 3)
 2338,06 (for category_id = 5)
 ....... (and for other category_id)

What I get now:

 1407,41 (only for category_id = 3)

My query does not add or display the sum of other category_id.

This is the query I am trying:

$query = "SELECT SUM(amount) AS TotalAmount FROM spendee WHERE type = 'Expense' 
group by category_id having count(*) >1 ";
    $expense_query = mysqli_query($connection, $query);
    $expense_count = mysqli_fetch_array($expense_query);
    echo $expense_count[0];

Been stuck with this for the last couple of days. Any help is very much appreciated. Thank you!

Answer 1

You're only calling mysqli_fetch_array() once. You need to call it in a loop to get all the totals. You should also include the category ID in the SELECT list.

$query = "SELECT category_id, SUM(amount) AS TotalAmount FROM spendee WHERE type = 'Expense' 
            group by category_id having count(*) >1 ";
$expense_query = mysqli_query($connection, $query);
while ($row = mysqli_fetch_assoc($expense_query)) {
    echo "{$row['TotalAmount']} (for category_id = {$row['category_id']}<br>\n";
}

Answer 2

The query here works. It's just that you only select the first result from the $expense_count variable. $expense_count[1] will return the second category listed, $expense_count[2 will return the third one, ect... Try echo implode(" <br>", $expense_count);

Have a nice day.