php中while循环中的分组和求和值

Question

我有一个从mysql数据库返回行列表的查询，生成的行列表中的行值是相同的。

Table
id    mAmount   paidAmount
1       100     50
1       100     30
2       200     20
2       200     150

我实际上想要对paidAmount求和，并从每个相同id的mAmount值中减去一个值。

例如

 1 |  (100) - (50 + 0)  = 50    |
 1 |  (100) - (30 + 50) = 20    |
 2 |  (200) - (20 + 0)  = 180   |
 2 |  (200) - (150 + 20) = 30   |

我不希望任何人给我的完整代码，但如何使用php的while循环或可能的foreach语句的想法。谢谢，真的很感谢。

Answer 1

只需循环并累加支付金额，然后进行减法。在本例中，我假设您按id对记录进行了预排序，并将记录传递给一个名为rows的多维数组：

$currentId = $rows[0]['id'];
$accumulated = 0;
foreach ( $rows as $row ) {
  if ( $row['id'] != $currentId ) {
    $accumulated = 0;
    $currentId = $row['id'];
  } // end if not current id

  $accumulated += $row['paidAmount'];
  $balance = $row['mAmount'] - $accumulated;
  $row['balance'] = $balance;
  $result[] = $row;
} // end foreach

print_r ( $result );

结果打印如下：

Array
(
    [0] => Array
        (
            [id] => 1
            [mAmount] => 100
            [paidAmount] => 50
            [balance] => 50
        )

    [1] => Array
        (
            [id] => 1
            [mAmount] => 100
            [paidAmount] => 30
            [balance] => 20
        )

    [2] => Array
        (
            [id] => 2
            [mAmount] => 200
            [paidAmount] => 20
            [balance] => 180
        )

    [3] => Array
        (
            [id] => 2
            [mAmount] => 200
            [paidAmount] => 150
            [balance] => 30
        )
    )