One, use aggregate function multi-table query and mongodbsimilar
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1. Definition
schemaconst mongoose = require('./db'); const OrderSchema = mongoose.Schema({ order_id: String, uid: Number, trade_no: String, all_price: Number, all_num: Number, }) module.exports = mongoose.model('Order', OrderSchema, 'order'); -
2. Query data
const OrderModel = require('./model/order'); OrderModel.aggregate([ { $lookup: { from: 'order_item', // 关联到的表 localField: 'order_id', // order表的字段 foreignField: 'order_id', // order_item表的字段 as: 'item' // 定义返回数据的字段 } }, { $match:{ "all_price":{ $gte:90}} } // ...继续写别的聚合函数 ], (err, docs) => { if (err) { console.log('查询错误'); } else { console.log(JSON.stringify(docs)); } })
2. order_itemQuery from data table to ordertable data
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1. Method 1 (complex method)
var mongoose=require('./db.js'); var OrderItemSchema=mongoose.Schema({ order_id:String, title:String, price:Number, num:Number }) module.exports=mongoose.model('OrderItem',OrderItemSchema,'order_item');// 先根据order_item的id去查找到当前的order_item数据,再根据order_id字段去order表查询数据 OrderItemModel.findOne({ "_id": "5b743da92c327f8d1b360546" }, function (err, docs) { var order_item = JSON.parse(JSON.stringify(docs)); var order_id = order_item.order_id; OrderModel.find({ "order_id": order_id }, function (err, order) { order_item[0].order_info = order[0]; console.log(order_item) }) }) -
2. Method two (use aggregate function)
const OrderModel = require('./model/order'); const OrderItemModel = require('./model/order_item'); const mongoose = require('mongoose'); // 从order_item查询到order表 OrderItemModel.aggregate([ // 使用多表的关联查询从order_item查询到order { $lookup: { from: 'order', localField: 'order_id', foreignField: 'order_id', as: 'order_info' } }, // 查询到的数据根据order表的id过滤 { $match:{ _id: mongoose.Types.ObjectId('5e0fd4bb08ad70786fd8ac87')} } ], (err, docs) => { if (err) { console.log('查询错误'); } else { console.log(JSON.stringify(docs)); } })
Two, mongoosecreate a one-to-many relationship inschema
The above method is just a dumb way to manually associate to the fields of the associated data table. The following describes
mongoose.Types.ObjectIdthe method used to associate other tables. Take the case:
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1. Create two tables for the relationship between teachers and students (the main functions are)
- There can be multiple students in a class
- Find all students through the class
- Inquiry through students to their class
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2. Create a class
schemaconst mongoose = require('./db'); const ClasssSchema = new mongoose.Schema({ name: { type: String, require: [true, '此项为必填内容'], }, // 定义班级下面的学生，因为一个班级可以是多个学生,所以可以定义为数组 students: [ { type: mongoose.Schema.Types.ObjectId, ref: 'student', } ] }); module.exports = mongoose.model('Classs', ClasssSchema, 'classs'); -
3. Define the student's
schemaconst mongoose = require('./db'); const StudentSchema = new mongoose.Schema({ name: { type: String, require: [true, '此项为必填内容'], }, age: Number, }); module.exports = mongoose.model('Student', StudentSchema, 'student'); -
4. Add student and class data
const ClasssModel = require('./model/classs'); const StudentModel = require('./model/student'); // 多次添加学生 const student = new StudentModel({ name: '马六', age: 35, }); student.save(); // 添加班级 const cls = new ClasssModel({ name: "初中一班", students: [ "5e129534c02d70632fd168dc", // id直接去数据库查看复制进去的 "5e1297c02069166b52e34ee4" ] }); cls.save(); -
5. Query all student information through the class
ClasssModel.aggregate([ { $lookup: { from: 'student', // 关联到学生表 localField: 'students', // 班级表中关联的字段 foreignField: '_id', // 学生表中被关联的id as: 'students', } } ], (err, docs) => { if (err) { console.log('查询错误', err); return } console.log(JSON.stringify(docs)); }) -
6. Inquire about their class through students
StudentModel.aggregate([ { $lookup: { from: 'classs', // 关联到班级表 localField: '_id', // 学生的id foreignField: 'students', // 关联到班级表中的字段 as: 'cls', } }, { $project: { "name": 1, "age": 1, "cls.name": 1 } } ], (err, docs) => { if (err) { console.log('查询错误', err); return } console.log(JSON.stringify(docs)); })
Three, use aggregate functions for three-table joint query
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1. The three tables are
- User table (one user may have multiple articles)
- Article table (an article can only have one author, but there can be multiple categories)
- Article classification table
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2. Define three
schema// category.js const mongoose = require('./db'); const CategorySchema = new mongoose.Schema({ title: String, }) module.exports = mongoose.model('Category', CategorySchema, 'category');// user.js var mongoose = require('./db.js'); var UserSchema = new mongoose.Schema({ name: String, age: Number, mobile: Number, status: { type: Number, default: 1 } }); module.exports = mongoose.model('User', UserSchema, 'user');// article.js const mongoose = require('./db'); const ArticleSchema = new mongoose.Schema({ title: String, category: [ { type: mongoose.Schema.Types.ObjectId, ref: 'category', } ], author: { type: mongoose.Schema.Types.ObjectId, ref: 'author', }, description: String, content: String, }); module.exports = mongoose.model('Article', ArticleSchema, 'article'); -
3. Create data
const CategoryModel = require('./model/category'); const UserModel = require('./model/user'); const ArticleModel = require('./model/article'); // 添加用户 const user = new UserModel({ name: '李四', age: 20, mobile: 120, }); user.save(); //添加分类 const category1 = new CategoryModel({ title: 'nodejs', }); const category2 = new CategoryModel({ title: 'python', }); const category3 = new CategoryModel({ title: 'nestjs', }); category1.save(); category2.save(); category3.save(); // 文章一 const article1 = new ArticleModel({ title: 'nest开发', category: [ '5e12a06bad979e89f8976851', // 从数据库中复制过来的 '5e129fd242616287b39dc55c', // 从数据库中复制过来的 ], author: '5e129f6bdc449e8610bdc1f8', // 从数据库中复制过来的 description: 'nestjs连接mongodb', content: '省去1000个字', }) article1.save(); // 文章二 const article2 = new ArticleModel({ title: 'python开发', category: [ '5e129fd242616287b39dc55d', // 从数据库中复制过来的 ], author: '5e129f7678a95b8648ebb471', // 从数据库中复制过来的 description: 'python基础开始', content: '省去1000个字', }) article2.save(); -
4. Query data in article table
// 根据文章表查询到文章、分类、作者 ArticleModel.aggregate([ { $lookup: { from: 'category', localField: 'category', foreignField: '_id', as: 'category', } }, { $lookup: { from: 'user', localField: 'author', foreignField: '_id', as: 'user', } }, ], (err, docs) => { if (err) { console.log('查询错误', err); return } console.log(JSON.stringify(docs)); })
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5. The user table queries the article
UserModel.aggregate([ { $lookup: { from: 'article', localField: '_id', foreignField: 'author', as: 'article', } }, ], (err, docs) => { if (err) { console.log('查询错误', err) return } console.log(JSON.stringify(docs)); })