php 如何使用PHP在第三列中减去两列输出
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how to subtract two columns output in a third column using PHP
提问by Jaime A
Using PHP I want to subtract each values of used column from credit column. I have created a tableA in phpmyadmin.
使用 PHP 我想从 credit 列中减去 used 列的每个值。我在 phpmyadmin 中创建了一个 tableA。
remaining:credit-used I can not get the results i just get same values of credit.
剩余：信用使用我无法得到结果我只是获得相同的信用值。
// The desire output in table A
id |date |credit |used|remaining|
1 |20-5-2013 |400 |300 |100 |
2 |19-5-2013 |300 |100 |200 |
3 |18-5-2013 |600 |50 |550 |
// db connection
query select all from tableA
$sql = "SELECT * FROM tableA";
$sql_result = mysql_query ($sql, $connection ) or die ('request "Could not execute SQL query" '.$sql);
?>
fetch the information and output into a table:
<table >
<tr>
bla bla..
</tr>
// echo:
<tr>
<td><?php echo $row["id"]; ?></td>
<td><?php echo $row["date"]; ?></td>
<td><?php echo $row["credit"]; ?></td>
<td><?php echo $row["used"]; ?></td>
I'm trying to do this query to get remaining:
我正在尝试执行此查询以获取剩余信息：
// <td> <?php> echo $total= $row["credit"] - $row["used"];?>
</td>
</tr>
</table>
can anyone give me a hints or highlight the error. Than you very much in advance.
任何人都可以给我提示或突出显示错误。比你提前很多。
采纳答案by aynber
You have a closing bracket on your php
你的 php 上有一个右括号
<td> <?php echo $row["credit"] - $row["used"]; ?> </td>
回答by Niet the Dark Absol
What you have should work, but why not let MySQL do the calculation?
你所拥有的应该可以工作，但为什么不让 MySQL 来计算呢？
mysql_query("SELECT *, `credit`-`used` AS `remaining` FROM `tableA`");
