[英]How can i Subtract from two Tables
我想从收入总额表中减去费用总额,但每次运行查询时都会得到一个错误的数字。
<?php
$query="SELECT income.Source
,SUM(income.Amount) as in_Amount
,SUM(expenses.Amount) as out_Amount
,SUM(income.Amount) - SUM(expenses.Amount) as total
FROM income as income
, expenses";
$result=mysql_query($query);
while($row=mysql_fetch_array($result)){
echo '<p class="stat"><span class="label label-danger">' . $row['total']. '</span> Naira Net Income</p>';
}
?>
收入表共有 40000,而费用表共有 5000,查询结果我得到 30000。
你正在做一个连接,你应该做子查询。 尝试这个:
SELECT Source, in_Amount, out_Amount, total_income - total_expenses FROM
(
SELECT income.Source, SUM(income.Amount) as in_Amount, SUM(expenses.Amount) as out_Amount,
( SELECT SUM(income.Amount) ) AS total_income,
( SELECT SUM(expenses.Amount) ) AS total_expenses
FROM income as income, expenses
) t
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