基于先前 MySQL 查询的算术计算

Question

我有一个带有“帐户”表的数据库，其中包含各种类型的交易。我成功地进行了查询以找到“总贷方”和“总借方”。我需要帮助来计算余额。即，如果“总贷方 > 总借方”答案应该是“余额 Cr”。否则，如果“总贷方

<?php
    $pp= ("SELECT SUM(amount) FROM account WHERE (mode='cash' AND type='payment') OR (mode='cash' AND type='purchase')");
    $total_pp = mysql_query($pp);
    while($gtotal_pp = mysql_fetch_array($total_pp)){
        echo "<table><tr><td>Total Credit</td><td>:</td><td>$</td><td align='right'>" . $gtotal_pp['SUM(amount)'] . "</td></tr>";
        echo "<br/>";
    }

    $sr = ("SELECT SUM(amount) FROM account WHERE (mode='cash' AND type='sale') OR (mode='cash' AND type='reciept')");
    $total_sr = mysql_query($sr);
    while($gtotal_sr = mysql_fetch_array($total_sr)){
        echo "<tr><td>Total Debit</td><td>:</td><td>$</td><td align='right'>" . $gtotal_sr['SUM(amount)'] . "</td></tr>";
    }

    $bgtotal_pp = $gtotal_pp['SUM(amount)'];
    $bgtotal_sr = $gtotal_sr['SUM(amount)'];
    $balance_cr = $bgtotal_pp - $bgtotal_sr;
    $balance_dr = $bgtotal_sr - $bgtotal_pp;

    if ($bgtotal_pp > $bgtotal_sr)
        echo "<tr><td>Balance (Cr.)</td><td>:</td><td>$</td><td align='right'>" . $balance_cr . "</td></tr></table>";

    else if ($bgtotal_pp < $bgtotal_sr)
        echo "<tr><td>Balance (Dr.)</td><td>:</td><td>$</td><td align='right'>" . $balance_dr . "</td></tr></table>";

    else
        echo"<tr><td>Balance</td><td>:</td><td></td><td align='right'>0.00</td></tr></table">;

    ?>

当

$bgtotal_pp = "(some number)";
$bgtotal_sr = "(some number");

代码完美运行。只有当我尝试带上一个查询而不是某个数字时，它总是显示“Else 语句”。

提前致谢。

Answer 1

这是关于查询，而不是 php 代码（有使用 mysql_ 等问题）。为什么要在应用程序中执行多个查询然后进行算术运算。您可以通过一个查询完成所有这些操作：

SELECT SUM(CASE WHEN mode = 'cash' and type in ('payment', 'purchase') then amount end) as Credit,
       SUM(CASE WHEN mode = 'cash' and type in ('sale', 'receipt') then amount end) as Debit,
       SUM(CASE WHEN mode = 'cash' and type in ('payment', 'purchase') then amount
                WHEN mode = 'cash' and type in ('sale', 'receipt') then - amount
                ELSE 0
           END) as Balance       
FROM account;

通常，我希望 where 子句或 group by 获取特定帐户的信息，但这不在您的原始数据中。