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[英]I have tables name as "expenses" and "orders" i want to get there total separately and then subtract orders total from expenses
[英]Selecting from two tables (sales/expenses) with the same column name (total)
我尝试了一些操作,到目前为止,这是唯一不引发错误的操作,但是结果不会在页面上回显,因此我不确定发生了什么。
$query = "SELECT SUM(sales.total) AS sales_total, SUM(expenses.total) AS expenses_total FROM sales,expenses";
其他所有东西都设置得很完美,我之前从未不必调用多个表。
例如,我如何在HTML中回显:
<? echo $row['SUM(sales_total)']; ?>
<? echo $row['SUM(expenses_total)']; ?>
谢谢!
编辑:附上我胡说八道的图片:)
这是笛卡尔联接,不会为您提供所需的结果。
$query = "SELECT SUM(sales.total) AS sales_total, SUM(expenses.total) AS expenses_total FROM sales,expenses";
您需要阅读内部联接才能正确执行此操作。 如果没有更多详细信息,除了进行两个查询(每个表一个)之外,我无法建议您如何解决该查询。 由于您要为每个字段指定一个AS子句,因此需要将回显修改为:
<? echo $row['sales_total']; ?>
<? echo $row['expenses_total']; ?>
希望有帮助!
更新:修改查询以产生所需的结果:
$query = "SELECT sales_summary.sales_total,
expenses_summary.expenses_total
FROM (SELECT SUM(sales.total) AS sales_total
FROM sales) sales_summary,
(SELECT SUM(expenses.total) AS expenses_total
FROM expenses) expenses_summary";
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