本文實(shí)例講述了MongoDB多表關(guān)聯(lián)查詢操作。分享給大家供大家參考，具體如下：

Mongoose的多表關(guān)聯(lián)查詢

首先，我們回憶一下，MySQL多表關(guān)聯(lián)查詢的語句：

student表：

calss表：

通過student的classId關(guān)聯(lián)進(jìn)行查詢學(xué)生名稱，班級的數(shù)據(jù)：

SELECT student.name,student.age,class.name FROM student,class WHERE student.classId = class.id

Mongoose多表聯(lián)合查詢(還是以眾所周知的學(xué)生、班級作為實(shí)例)

? 表結(jié)構(gòu)的定義(schemas目錄下)

1. student表(student.js)

var mongoose = require('mongoose');var Schema = mongoose.Schema;/*定義數(shù)據(jù)模式*/var StudentSchema = new mongoose.Schema({  name: String,  calssId: {    type: Schema.Types.objectId,    ref: 'class'  },  age: Number,  number: Number,  meta: {    createAt: {      type: Date,      default: Date.now()    },    updateAt: {      type: Date,      default: Date.now()    }  }  /*更新時(shí)間的*/});module.exports = StudentSchema;

2. class表(class.js)

var mongoose = require('mongoose');var Schema = mongoose.Schema;/*定義數(shù)據(jù)模式*/var ClassSchema = new mongoose.Schema({  name: String,  meta: {    createAt: {      type: Date,      default: Date.now()    },    updateAt: {      type: Date,      default: Date.now()    }  }  /*更新時(shí)間的*/});module.exports = ClassSchema;

? 生成Model（model目錄下）

1. student Model（student.js）

var mongoose = require('mongoose');var StudentSchema = require('../schemas/student');/*通過model編譯模式為模型*/var Student = mongoose.model('student', StudentSchema);/*導(dǎo)出Student模型 模塊*/module.exports = Student;

2. class Model（class.js）

var mongoose = require('mongoose');var ClassSchema = require('../schemas/class');/*通過model編譯模式為模型*/var Class = mongoose.model('class', ClassSchema);/*導(dǎo)出Class模型 模塊*/module.exports = Class;

? Model進(jìn)行數(shù)據(jù)的查詢操作

1. 將靜態(tài)類的方法加到Model的編譯中

StudentSchema.static = {  fetch: function(cb){ return this   .find({})   .sort('meta.updateAt') //按更新的時(shí)間排序  }}

2. 將靜態(tài)類方法加到Model中

StudentSchema.static('fetch', function(cb){   return this     .find({}, cb)  .sort('meta.updateAt')})

3. 直接調(diào)用model的find()方法

查詢的結(jié)果均為：

[
    {
        _id: '5a05222f583e5720b8660191',
        name: '張三',
        age: 18,
        number: 11,
        classId: '5a0036512b740f32e4371e66'
    },
    {
        _id: '5a05222f583e5720b8660091',
        name: '李四',
        age: 19,
        number: 11,
        classId: '5a0036512b740f32e1371e66'
    },
    {
        _id: '5a05222f583e5720b18660191',
        name: '趙五',
        age: 17,
        number: 11,
        classId: '5a0036512b7420f32e4371e66'
    }
]

? 多表聯(lián)合查詢（學(xué)生對應(yīng)班級）

StudentSchema.static = {  findStudentWithClass: function (cb) {    return this      .find({})      .populate('classId')//注意這是聯(lián)合查詢的關(guān)鍵      .sort('meta.updateAt')      .exec(cb)  }}

查詢結(jié)果：

[
    {
        _id: '5a05222f583e5720b8660191',
        name: '張三',
        age: 18,
        number: 11,
        classId: {
            _id: '5a0036512b740f32e4371e66',
            name: '一年1班'
        }
    },
    {
        _id: '5a05222f583e5720b8660091',
        name: '李四',
        age: 18,
        number: 11,
        classId: {
            _id: '5a0036512b740f32e1371e66',
            name: '二年2班'
        }
    },
    {
        _id: '5a05222f583e5720b18660191',
        name: '趙五',
        age: 18,
        number: 11,
        classId: {
            _id: '5a0036512b7420f32e4371e66',
            name: '一年2班'
        }
    }
]

? 由上面的實(shí)例可知，mongoose的多表聯(lián)合查詢的關(guān)鍵：

1. 數(shù)據(jù)模式結(jié)構(gòu)定義需要利用關(guān)鍵字ref定義關(guān)聯(lián)

var Schema = new mongoose.Schema({  field: { type: mongoose.Schema.Type.ObjectId, ref: 'model'  }});Schema.static = {  fetch: function(cb){ return this    .find({})    .populate('field')    .exec(cb) } }var Model = mongoose.Model('model',Schema );

希望本文所述對大家MongoDB數(shù)據(jù)庫程序設(shè)計(jì)有所幫助。