在查询中添加两个值的和

Question

所以我做了一个查询，得到以下结果

 +---------------+---------------+---------+---------
 | payID         | payRate       | hours   | Earnings
 +---------------+---------------+---------+--------
 |  entertainment| 12            |      18 | 216
 |        retail | 10            |      28 | 280
 +---------------+---------------+---------+----------

查询和代码的其他部分如下：

 $query = "SELECT jobId, payRate, SUM(hours) AS 'All_Hours' ,payRate * SUM(hours) AS 'total'
                       FROM users INNER JOIN deposit ON userId = empId
                      WHERE users.email = '" . $_SESSION['email'] ."' 
                      GROUP BY jobId,payRate";



                      $result = mysqli_query($db, $query); //we make the query

                  if (!$result) { //if the query failed
                   echo("<p id = 'greatideadescription'>
                              Error, the query could not be executed: " .
                   mysqli_error($db) . "</p>");
                   mysqli_close($db);}

                if (mysqli_num_rows($result) == 0) { //if no rows returned
                   echo("<tr><td />
                               <td>No Results</td>
                               <td /></tr>");
                   mysqli_close($db); //close the database
                   exit("</table></div></form></div></div>
                               <script>DisplayFooter();</script></body></html>");
                        } 
                       $numRows = mysqli_num_rows($result); //gets number of rows
                       $numFields = mysqli_num_fields($result); //gets number of fields
                       //prints the data in the table
                       PrintTable($result, $numRows, $numFields);

函数PrintTable如下

 function PrintTable($result, $numRows, $numFields) {
  $row = mysqli_fetch_row($result); //fetches the first row
  for ($i = 0; $i < $numRows; $i++) {
  echo("<tr>"); //opens a new row

  for ($j = 0; $j < $numFields; $j++) { //second loop goes through columns
  echo("<td>" . $row[$j] . "</td>"); 
   } //end inner for loop

   $row = mysqli_fetch_row($result); //fetches subsequent rows
   echo("</tr>"); //closes the row
   } //end outer for loop
  } 

我想要的是回显收入的总和，在这种情况下，它将是496。我该怎么做？

Answer 1

如果您知道总和列的列索引，则可以尝试如下操作：

function PrintTable($result, $numRows, $numFields) {
    $total = 0; // Initialize variable before going through each row
    $row = mysqli_fetch_row($result); //fetches the first row
    for ($i = 0; $i < $numRows; $i++) {
        echo("<tr>"); //opens a new row

        for ($j = 0; $j < $numFields; $j++) { //second loop goes through columns
            echo("<td>" . $row[$j] . "</td>");
            if($j == 3)
              $total += $row[$j];
        } //end inner for loop

        $row = mysqli_fetch_row($result); //fetches subsequent rows
        echo("</tr>"); //closes the row
    } //end outer for loop
}

之后，您可以使用总计或将其返回到您的主代码中以在关闭表或或或之后回显它。

更好的方法是进行3个更改：

1. payRate * SUM(hours) AS earnings在您的sql语句中，稍后您将使用该名称
2. 使用mysqli_fetch_assoc获取一个关联数组，您可以在其中按名称访问列（ $row['earnings'] ）
3. 对列使用foreach循环，因为您没有可以迭代的索引

使用哪种方式取决于您...