SELECT COUNT表示數據庫中的列？

Question

如何計算表中與相關條件匹配的行數和計數的echo。

代碼如下::

<?php 
     $sql = "SELECT * FROM input ORDER BY date DESC";
     $result = $conn->query($sql);

     if ($result->num_rows > 0) { 
     while($row = $result->fetch_assoc()) { 
     $myid = $row["id"] ;
 $sql3 = "SELECT COUNT question_id FROM output WHERE question_id = $myid";
    $result3 = $conn->query($sql3);
?>

<div id="q">

        <small><p><?php echo $row["date"]; ?></p></small>
        <p id="tag3"><small><?php echo $result3['']; ?></small></p>
</div>

任何建議將不勝感激..

Answer 1

您需要使用COUNT（question_id）函數，如下所示

    $sql3 = "SELECT COUNT(question_id ) as  TotalQuestions FROM output WHERE question_id = $myid";
 $result3 = $conn->query($sql3);

然后從上面的查詢中獲取結果使用fetch_fieled（）

while ($info = $result3->fetch_field()) {
$TotalCount = $info->TotalQuestions ;
}

然后顯示值

<small><?php echo $TotalCount ; ?></small

Answer 2

報價遺失

$sql3 = "SELECT * question_id FROM output WHERE question_id = '".$myid."'";

其次，我沒有看到關閉括號

<?php 
     $sql = "SELECT * FROM input ORDER BY date DESC";
     $result = $conn->query($sql);

     if ($result->num_rows > 0) { 
     while($row = $result->fetch_assoc()) { 
     $myid = $row["id"] ;
$sql3 = "SELECT COUNT(*) as rowCount FROM output WHERE question_id = '".$myid."'";
    $result3 = $conn->query($sql3);
$rowCount= $result3->fetch_assoc();
?>

<div id="q">

        <small><p><?php echo $row["date"]; ?></p></small>
        <p id="tag3"><small><?php echo $rowCount['rowCount']; ?></small></p>
</div>
<?php }//while

} //if 

?>

Answer 3

嘗試這個

 $sql3 = "SELECT COUNT(1) as row_count FROM output WHERE question_id = ".$myid."";
 $result3 = $conn->query($sql3);
 $row_count = $result3->fetch_assoc();

 echo $row_count['row_count'];