mysql - 如何使用子查询进行进一步的计算？

Question

如何创建子查询以进一步计算 DATEDIFF(包括另一列(金额))并同时输出 DATEDIFF 和 X？

例如。 ddate*金额/365*0.1 = X

$result = mysqli_query($con,"SELECT *,
          DATEDIFF(mdate,pdate)
          AS ddate 
          FROM contacts
          WHERE DATEDIFF(mdate,pdate)");

while($row = mysqli_fetch_array($result)) {
    echo "<td>" . $row['ddate'] . "</td>";
    }

Answer 1

直接执行即可，无需子查询:

 $result = mysqli_query($con,"SELECT DATEDIFF(mdate,pdate) as NoOfDays,
      (DATEDIFF(mdate,pdate) * amount) / 365 * 0.1 as XAmount
      FROM contacts
      WHERE DATEDIFF(mdate,pdate)>=1");