MySQL Query 在 NodeJS 端点只返回一行而不是所有行？答案

【问题标题】：MySQL Query returns Just One Row instead of All Rows at NodeJS Endpoint?MySQL Query 在 NodeJS 端点只返回一行而不是所有行？
【发布时间】：2021-05-13 10:47:24
【问题描述】：

我有这个 NodeJS 端点，它应该从 MySQL 数据库中获取对帖子编号 201 的所有回复。

 http://mysite:3000/getreplies/201

这是创建端点的 NodeJS 代码；

app.get("/getreplies/:repliesId", audioposts.findReplies);

exports.findReplies = (req, res) => {
  Audiopost.findByOpId(req.params.repliesId, (err, data) => {
    if (err) {
      if (err.kind === "not_found") {
        res.status(404).send({
          message: `Not found Replies with id ${req.params.repliesId}.`
        });
      } else {
        res.status(500).send({
          message: "Error retrieving Audiopost with id " + req.params.audiopostId
        });
      }
    } else res.send(data);
  });
};

这是 MySQL 选择查询；

Audiopost.findByOpId = (repliesId, result) => {
  sql.query(`  
   SELECT
    ap.audioname, 
    ap.userid, 
    ap.audioid, 
    ap.title, 
    ap.likes,
    ap.opid,    
    u.gavatar, 
    u.name, 
    u.email,
       (
        SELECT GROUP_CONCAT(t.tagname)
        FROM entitytag et
        LEFT JOIN tags t on t.tagid = et.tagid
        WHERE et.audioid = ap.audioid
    ) tagname,
    (
      select count(*) from audioposts AS apost WHERE apost.opid = ap.audioid
    ) as replycount
FROM audioposts ap 
LEFT JOIN users u ON u.id = ap.userid
WHERE ap.opid = ${repliesId}  
  `, (err, res) => {
    if (err) {
      console.log("error: ", err);
      result(err, null);
      return;
    }

    if (res.length) {
      console.log("found audiopost: ", res[0]);
      result(null, res[0]);
      return;
    }
      result({ kind: "not_found" }, null);
  });
};

查询本身似乎很好。但是为什么端点只返回第一行而不是所有行呢？

【问题讨论】：

标签： mysql node.js endpoint

【解决方案1】：

    Audiopost.findByOpId = (repliesId, result) => {
  sql.query(`  
   SELECT
    ap.audioname, 
    ap.userid, 
    ap.audioid, 
    ap.title, 
    ap.likes,
    ap.opid,    
    u.gavatar, 
    u.name, 
    u.email,
       (
        SELECT GROUP_CONCAT(t.tagname)
        FROM entitytag et
        LEFT JOIN tags t on t.tagid = et.tagid
        WHERE et.audioid = ap.audioid
    ) tagname,
    (
      select count(*) from audioposts AS apost WHERE apost.opid = ap.audioid
    ) as replycount
FROM audioposts ap 
LEFT JOIN users u ON u.id = ap.userid
WHERE ap.opid = ${repliesId}  
  `, (err, res) => {
    if (err) {
      console.log("error: ", err);
      result(err, null);
      return;
    }

    if (res.length) {
     
      result(null, res);
      return;
    }
      result({ kind: "not_found" }, null);
  });
};

【讨论】：