摘要：實(shí)現(xiàn)代碼最近在做一個(gè)項(xiàng)目涉及到的關(guān)聯(lián)查詢(xún)等等，之前做的，比較多，而用的都是比較簡(jiǎn)單的存儲(chǔ)數(shù)據(jù)，簡(jiǎn)單查詢(xún)等等。

實(shí)現(xiàn)代碼github
最近在做一個(gè)項(xiàng)目涉及到mongoose的關(guān)聯(lián)查詢(xún)等等，之前做的mysql，postgresql比較多，而mongoose用的都是比較簡(jiǎn)單的存儲(chǔ)數(shù)據(jù)，簡(jiǎn)單查詢(xún)等等。
剛開(kāi)始涉及ref還是有點(diǎn)小暈的，查詢(xún)了相關(guān)資源，也可以模模糊糊做出來(lái)，但是會(huì)有各種報(bào)錯(cuò)。痛下決心研究透徹點(diǎn)，晚上熬夜到2點(diǎn)終于有點(diǎn)小眉目了。

node v8.5.0
mongodb
結(jié)合一個(gè)接口理解
結(jié)合promise-async-await
一般采用mvc模式，本文就直接在express里直接寫(xiě)了

直接使用了express -e mongoose-ref

const mongoose = require("mongoose");
mongoose.connect("mongodb://localhost:27017/ref");

同時(shí)建立關(guān)聯(lián)user->city->state->country

  const Schema = mongoose.Schema;
  const ObjectId = Schema.Types.ObjectId;
  const UserSchema = new Schema({
    username: { type: String },
    userpwd: { type: String },
    userage: { type: Number },
    city: { type: Schema.Types.ObjectId, ref: "City" },
  });
  const CitySchema = new Schema({
    name: { type: String },
    state: { type: Schema.Types.ObjectId, ref: "State" }
  });
  const StateSchema = new Schema({
    name: { type: String },
    country: { type: Schema.Types.ObjectId, ref: "Country" }
  });
  const CountrySchema = new Schema({
    name: { type: String }
  });
  const User = mongoose.model("User", UserSchema);
  const City = mongoose.model("City", CitySchema);
  const State = mongoose.model("State", StateSchema);
  const Country = mongoose.model("Country", CountrySchema);

  const user_getCountryList = async function (req, res) {
    console.log("/v1/ref start -->" + JSON.stringify(req.body));
    try {
      const respondData = {
        status: res.statusCode,
        data: {},
        error: {}
      };
      const username = req.body.username;
      const userpwd = req.body.userpwd;
      const userage = req.body.userage;
      const usercityname = req.body.usercityname;
      const userstatename = req.body.userstatename;
      const usercountryname = req.body.usercountryname;
      const userInfoCountry = await findUserCountry({ name: usercountryname }, usercountryname);//查看國(guó)家
      const userInfoState = await findUserState({ name: userstatename }, userstatename);//查看州
      const userInfoCity = await findUserCity({ name: usercityname }, usercityname);//查看城市
      const userInfo = await findUser({ username: username, }, username,userpwd,userage);//查看用戶信息
      const updateInfoUser = await updateUser({ _id: userInfo },userInfoCity);//更新用戶信息
      const updateInfoCity = await updateCity({ _id: userInfoCity }, userInfoState);//更新城市信息
      const updateInfoState = await updateState({ _id: userInfoState }, userInfoCountry);//更新州信息
      return res.json(respondData);
    }
    catch (error) {
      //錯(cuò)誤處理
      console.log("userCity error -->" + JSON.stringify(error));
      respondData.error = error;
      return res.json(respondData);
    }
  }

首先查看傳入的國(guó)家在country中有沒(méi)有，加入有，返回_id,沒(méi)有就創(chuàng)建傳入的國(guó)家名，并返回_id,查看findUserCountry函數(shù)對(duì)應(yīng)的邏輯

  const findUserCountry = async function (cnd, country) {
    console.log("findUserCountry start --> " + JSON.stringify(cnd));
    return new Promise(function (resolve, reject) {
      Country.findOne(cnd, function (error, data) {
        console.log("findUserCountry findOne  data --> " + JSON.stringify(data));
        if (error) {
          return reject(error);
        }
        if (data) {
          return resolve(data._id);
        } else {
          const userCountry = new Country({
            name: country
          });
          userCountry.save(function (err, data) {
            if (err) {
              console.log("userCountry.save err-->" + JSON.stringify(err));
              return reject(err);
            }
            console.log("userCountry-->" + JSON.stringify(data));
            return resolve(data._id);
          });
        }
      });
    })
  }

同理傳入的州，城市，用戶信息以同樣的方式返回_id

通俗的說(shuō)就是在User表中city保存City表中所需要的_id;也就是之前返回的_id這時(shí)就可以用到，可以參考updateUser函數(shù)

   const updateUser = async function (cnd, cityid) {
    console.log("updateUser start --> " + JSON.stringify(cnd));
    return new Promise(function (resolve, reject) {
      User.update(cnd, { $set: { city: cityid } }, function (error, data) {
        console.log("updateUser findOne  data --> " + JSON.stringify(data));
        if (error) {
          return reject(error);
        }
        return resolve(data);
      });
    })
  }

可以使用postman模擬數(shù)據(jù)，如圖：

這時(shí)就把City對(duì)應(yīng)的_id寫(xiě)進(jìn)了User表中，可以查看表，如圖：


同理user->city->state->country數(shù)據(jù)都可以寫(xiě)進(jìn)不同的表中。

當(dāng)傳入username 時(shí),使用populate關(guān)聯(lián)查詢(xún),可以查詢(xún)出這個(gè)人的所以信息

 User.find({ username: user_name })
    .populate("city")
    .exec(function (err, docs) {
      City.find({ _id: docs[0].city._id })
        .populate("state")
        .exec(function (err, doc) {
          State.find({ _id: doc[0].state._id })
            .populate("country")
            .exec(function (err, result) {
              const userInfo = {};
              userInfo.username = docs[0].username;
              userInfo.userpwd = docs[0].userpwd;
              userInfo.userage = docs[0].userage;
              userInfo.usercity = doc[0].name;
              userInfo.userstate = result[0].name;
              userInfo.usercountry = result[0].country.name;
              respondData.data.push(userInfo);
              return res.json(respondData);
            })
        })
    });

使用postman模擬接口如下