SQL 循环内的 PHP/SQL 查询表

Question

在循环响应之前，您必须检查它的长度。没有检查这段代码，但它应该工作

var len = response.length;

$("#sel_zone").empty();

if(len == 0){

    $("#sel_zone").append('<option value="">No Data Found</option>');

} else{

    for( var i = 0; i<len; i++){

        var id = response[i]['id'];

        var name = response[i]['name'];

        $("#sel_zone").append("<option value='"+id+"'>"+name+"</option>");

    }

}

Answer 1

&nbsp; &nbsp; 只要有可能，您应该避免在循环中使用 SQL，并尝试一次性获取所有数据。在这种情况下，您可以JOIN在第一条语句中使用获取用户名。就我个人而言，我还会只列出您想要获取的列，而不是使用*...$sql = "SELECT t1.id as messageID, t1.from_id, t2.full_name, t2.title&nbsp;&nbsp; &nbsp; &nbsp; &nbsp; FROM table1 t1&nbsp; &nbsp; &nbsp; &nbsp; JOIN table2 t2 on t2.id = t1.user_id&nbsp; &nbsp; &nbsp; &nbsp; WHERE t1.user_id = '$userid' AND t1.unread = 0";&nbsp;$result = $conn->query($sql);&nbsp;if ($result->num_rows > 0) {&nbsp;&nbsp; &nbsp; while($row = $result->fetch_assoc()) {;&nbsp;&nbsp; &nbsp; &nbsp; &nbsp; $from = $row["from_id"];&nbsp;&nbsp; &nbsp; &nbsp; &nbsp; $messageID = $row["messageID"];&nbsp;&nbsp; &nbsp; &nbsp; &nbsp; ?>&nbsp; &nbsp; &nbsp; &nbsp; <tr>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <td><?php&nbsp; echo $row['full_name'];?></td>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <td><?php echo $row["title"];?></td>&nbsp; &nbsp; &nbsp; &nbsp; </tr>&nbsp; &nbsp; &nbsp; &nbsp; <?php&nbsp;&nbsp; &nbsp; }}&nbsp;无法测试它，但应该更有用。