Javascript 一对多关系节点Js

我正试图根据当前登录用户的会话id从中选择所有照片

我有一个照片表，用于跟踪每个用户的照片

身份证| 用户照片| 用户id（外键）

当我运行代码时，我不断收到这样的错误消息“发送到客户端后无法设置头”。我做错了什么？我需要在这里加入用户表吗？任何帮助都将不胜感激

“发送到客户端后无法设置标题。”表示您试图向用户发送多个响应，请使用此功能

res.json(rows.map(function (row) { return row.user_photos }))

---

您不能从循环发送响应，因为它是第一次发送响应，然后给出错误。 请试试这个-

let select_photos_sql = "SELECT * FROM photos WHERE user_id = ?";
 mysql_connection.query(select_photos_sql, [session_id], function (error, 
rows) {
if(error){
    res.send("An error has occurred, please try again later.");
} else {

    if(rows.length > 0){ /**IS THIS BLOCK NECESSARY? WHEN I CHANGE IT TO === 1, I DON'T GET THE 
                            ERROR BUT I GET NO PHOTOS FOUND**/
        var photos_arr = [];
        var photo_count = 0;
        rows.forEach(function (row) {

            let photos = row.user_photos;

            console.log(photos); /**LOGS OUT THE PHOTOS FROM THE USER BUT CAN'T DISPLAY IT**/
            photos_arr.push(photos);
            photo_count = photo_count+1;
        });
        if (photo_count == rows.length) {
            res.render("user_photos", {photos: photos_arr});
        }

    } else {
        res.send("No photos found.");
    }
}
});

---

尝试将

res.render

从循环中删除。非常感谢您的帮助！顺便问一下，您知道如何在html图像标记中输出用户的图像吗？我在.ejs文件上有一个图像标记，但当它输出结果时，它输出为：image1，image2。然后，如果我在src中放置一个带有结果的图像标记，它将是。有没有一种方法可以让它变成某种循环？

let select_photos_sql = "SELECT * FROM photos WHERE user_id = ?";
 mysql_connection.query(select_photos_sql, [session_id], function (error, 
rows) {
if(error){
    res.send("An error has occurred, please try again later.");
} else {

    if(rows.length > 0){ /**IS THIS BLOCK NECESSARY? WHEN I CHANGE IT TO === 1, I DON'T GET THE 
                            ERROR BUT I GET NO PHOTOS FOUND**/
        var photos_arr = [];
        var photo_count = 0;
        rows.forEach(function (row) {

            let photos = row.user_photos;

            console.log(photos); /**LOGS OUT THE PHOTOS FROM THE USER BUT CAN'T DISPLAY IT**/
            photos_arr.push(photos);
            photo_count = photo_count+1;
        });
        if (photo_count == rows.length) {
            res.render("user_photos", {photos: photos_arr});
        }

    } else {
        res.send("No photos found.");
    }
}
});