php和mysql中的双和

我有一个名为“homeworks”的Mysql表，我想得到一行的总数，所以我使用以下代码得到结果：

$homeworks_sum_sqli = "SELECT sum(lhid) AS result FROM homeworks WHERE lhid='".$row['lessons_id']."'";
$homeworks_sum_query = mysqli_query($connect, $homeworks_sum_sqli);
$rowsum = mysqli_fetch_array($homeworks_sum_query);
$sum = $rowsum['result'];
echo "$sum";

问题是，结果是您在图片中看到的某些行加倍了！！ 我怎样才能解决这个问题？

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谢谢：）

经过长时间的搜索，我找到了答案：）

我替换了这个代码

$homeworks_sum_sqli = "SELECT sum(lhid) AS result FROM homeworks WHERE lhid='".$row['lessons_id']."'";

$homeworks_sum_sqli = "SELECT COUNT(lhid) AS result FROM homeworks WHERE lhid='".$row['lessons_id']."'";

将其写入此代码

$homeworks_sum_sqli = "SELECT sum(lhid) AS result FROM homeworks WHERE lhid='".$row['lessons_id']."'";

$homeworks_sum_sqli = "SELECT COUNT(lhid) AS result FROM homeworks WHERE lhid='".$row['lessons_id']."'";

总和->计数

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就是这样：）

lhid列是自动递增的吗？不，它是用于课程的。idlhid是主键还是唯一列？不，我只是使用此列记录另一个表中的课程id。