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This blog post is for my own reference. This is why there is not much explanation.
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Create a course model

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const mongoose = require("mongoose")\n\nconst courseSchema = new mongoose.Schema({\n  name: String,\n  author: String,\n  tags: [String, String],\n  isPublished: Boolean,\n  price: Number,\n})\n\nconst Course = mongoose.model("Course", courseSchema)\n\nmodule.exports = Course
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Create courses

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const mongoose = require("mongoose")\nconst dotenv = require("dotenv")\nconst connectDB = require("./config/db")\nconst Course = require("./models/courses")\n\ndotenv.config()\n\nconnectDB()\n\nconst createCourses = async () => {\n  const course = new Course({\n    name: "Full-stack Web Development",\n    author: "Hemanta Sundaray",\n    tags: ["React", "Node"],\n    isPublished: true,\n  })\n\n  const result = await course.save()\n  console.log(result)\n}\n\ncreateCourses()
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find

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const getCourses = async () => {\n  const courses = await Course.find()\n\n  console.log(courses)\n}\n\ngetCourses()
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[\n   {\n     tags: [ 'React', 'Node' ],\n     _id: 60b49c4dba4e232500b7df88,\n     name: 'Full-stack Web Development',\n     author: 'Hemanta Sundaray',\n     price: 40,\n     isPublished: true,\n     __v: 0\n   },\n   {\n     tags: [ 'Frontend', 'Static site generator' ],\n     _id: 60b49d1e5924cd498468bdde,\n     name: 'Gatsby',\n     author: 'Hemanta Sundaray',\n     price: 30,\n     isPublished: true,\n     __v: 0\n   },\n   {\n     tags: [ 'Backend', 'Database' ],\n     _id: 60b49db34efdc80fe0c493c0,\n     name: 'Master Mongoose',\n     author: 'Hemanta Sundaray',\n     price: 20,\n     isPublished: true,\n     __v: 0\n   }\n]
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We can also filter our query by passing an objet of key-value pairs to the find method.

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const getCourses = async () => {\n  const courses = await Course.find({\n    isPublished: false,\n  })\n\n  console.log(courses)\n}\n\ngetCourses()
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[]
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All of the courses have been published, which is why we got an empty array.

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findById

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const getCourse = async () => {\n  const course = await Course.findById("60b49d1e5924cd498468bdde")\n\n  console.log(course)\n}\n\ngetCourse()
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{\n   tags: [ 'Frontend', 'Static site generator' ],\n   _id: 60b49d1e5924cd498468bdde,\n   name: 'Gatsby',\n   author: 'Hemanta Sundaray',\n   price: 30,\n   isPublished: true,\n   __v: 0\n }
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select

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We can select specific properties with the select method.

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const getCourses = async () => {\n  const courses = await Course.find().select({\n    name: 1,\n  })\n\n  console.log(courses)\n}\n\ngetCourses()
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 [\n    { _id: 60b49c4dba4e232500b7df88, name: 'Full-stack Web Development' },\n    { _id: 60b49d1e5924cd498468bdde, name: 'Gatsby' },\n    { _id: 60b49db34efdc80fe0c493c0, name: 'Master Mongoose' }\n]
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sort

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We can sort the results with the sort method. 1 represents ascending order and -1 represents descending order.

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const getCourses = async () => {\n  const courses = await Course.find().select({ name: 1 }).sort({\n    price: 1,\n  })\n\n  console.log(courses)\n}\n\ngetCourses()
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[\n    { _id: 60b49db34efdc80fe0c493c0, name: 'Master Mongoose' },\n    { _id: 60b49d1e5924cd498468bdde, name: 'Gatsby' },\n    { _id: 60b49c4dba4e232500b7df88, name: 'Full-stack Web Development' }\n]
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update

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const updateCourse = async id => {\n  const course = await Course.findById(id)\n  if (!course) return\n  course.name = "Intermediate Gatsby"\n  const result = await course.save()\n  console.log(result)\n}\n\nupdateCourse("60b49d1e5924cd498468bdde")
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{\n   tags: [ 'Frontend', 'Static site generator' ],\n   _id: 60b49d1e5924cd498468bdde,\n   name: 'Intermediate Gatsby',\n   author: 'Hemanta Sundaray',\n   price: 30,\n   isPublished: true,\n   __v: 0\n}
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delete

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deleteOne

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const deleteCourse = async id => {\n  const result = await Course.deleteOne({\n    _id: id,\n  })\n  console.log(result)\n}\n\ndeleteCourse("60b49db34efdc80fe0c493c0")
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{\n   n: 1,\n   opTime: {\n     ts: Timestamp { _bsontype: 'Timestamp', low_: 2, high_: 1622462068 },\n     t: 50\n   },\n   electionId: 7fffffff0000000000000032,\n   ok: 1,\n   '$clusterTime': {\n     clusterTime: Timestamp { _bsontype: 'Timestamp', low_: 2, high_: 1622462068 },\n     signature: { hash: [Binary], keyId: [Long] }\n   },\n   operationTime: Timestamp { _bsontype: 'Timestamp', low_: 2, high_: 1622462068 },\n   deletedCount: 1\n }
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deleteOne method does not return the deleted object. If we want the deleted object to be returned, we can use the findByIdAndRemove method.

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findByIdAndRemove

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const deleteCourse = async id => {\n  const course = await Course.findByIdAndRemove(id)\n  console.log(course)\n}\n\ndeleteCourse("60b49c4dba4e232500b7df88")
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{\n   tags: [ 'React', 'Node' ],\n   _id: 60b49c4dba4e232500b7df88,\n   name: 'Full-stack Web Development',\n   author: 'Hemanta Sundaray',\n   price: 40,\n   isPublished: true,\n   __v: 0\n}
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Comparison query operators

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In MongoDB we have some standard operators for comparing values. Since, mongoose is built on top of mongoDB driver, these operators are also available in mongoose.

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$gt

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const getCourses = async () => {\n  const courses = await Course.find({\n    price: { $gt: 20 },\n  })\n\n  console.log(courses)\n}\n\ngetCourses()
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[\n   {\n     tags: [ 'React', 'Node' ],\n     _id: 60b49c4dba4e232500b7df88,\n     name: 'Full-stack Web Development',\n     author: 'Hemanta Sundaray',\n     price: 40,\n     isPublished: true,\n     __v: 0\n   },\n   {\n     tags: [ 'Frontend', 'Static site generator' ],\n     _id: 60b49d1e5924cd498468bdde,\n     name: 'Gatsby',\n     author: 'Hemanta Sundaray',\n     price: 30,\n     isPublished: true,\n     __v: 0\n   }\n]
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$in

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const getCourses = async () => {\n  const courses = await Course.find({\n    price: { $in: [50, 40, 60] },\n  })\n\n  console.log(courses)\n}\n\ngetCourses()
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[\n   {\n     tags: [ 'React', 'Node' ],\n     _id: 60b49c4dba4e232500b7df88,\n     name: 'Full-stack Web Development',\n     author: 'Hemanta Sundaray',\n     price: 40,\n     isPublished: true,\n     __v: 0\n   }\n]
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Logical query operators

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or

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Find the courses that are not published or priced at 30.

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const getCourses = async () => {\n  const courses = await Course.find().or([\n    { price: 30 },\n    { isPublished: false },\n  ])\n\n  console.log(courses)\n}\n\ngetCourses()
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[\n   {\n     tags: [ 'Frontend', 'Static site generator' ],\n     _id: 60b49d1e5924cd498468bdde,\n     name: 'Gatsby',\n     author: 'Hemanta Sundaray',\n     price: 30,\n     isPublished: true,\n     __v: 0\n   }\n]
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