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MongoDB

Mongodb learning

MongoDB Database Operations Tutorial

MongoDB Operations Examples

This guide covers essential MongoDB operations with practical examples. Each section includes command usage with sample outputs.

Table of Contents

Database and Collection Setup

Creating a Database

test> use Exercise-1;
switched to db Exercise-1

Creating Collections

Exercise-1> db.createCollection("Users");
{ ok: 1 }
Exercise-1> db.createCollection("Products");
{ ok: 1 }
Exercise-1> db.createCollection("Orders");
{ ok: 1 }
Exercise-1> db.createCollection("Payments");
{ ok: 1 }

Basic CRUD Operations

Inserting Documents

db.Users.insertMany([
  { "u_id": 1, "name": "Kathir", "city": "Madurai" },
  { "u_id": 2, "name": "Jeeva", "city": "Paramakudi" },
  { "u_id": 3, "name": "Arun", "city": "Chennai" },
  { "u_id": 4, "name": "Mohan", "city": "Coimbatore" },
  { "u_id": 5, "name": "Ravi", "city": "Trichy" }
]);

db.Products.insertMany([
  { "p_id": 101, "name": "Pen", "price": 20, "category": "Stationery", "stock": 25 },
  { "p_id": 102, "name": "Headphone", "price": 500, "category": "Electronics", "stock": 10 },
  { "p_id": 103, "name": "Carrot", "price": 25, "category": "Vegetables", "stock": 100 },
  { "p_id": 104, "name": "Notebook", "price": 50, "category": "Stationery", "stock": 30 },
  { "p_id": 105, "name": "Mouse", "price": 400, "category": "Electronics", "stock": 15 }
]);

db.Orders.insertMany([
  { "o_id": 1000, "u_id": 2, "p_id": 101, "qty": 3, "status": "Pending" },
  { "o_id": 1005, "u_id": 2, "p_id": 103, "qty": 25, "status": "Delivered" },
  { "o_id": 1010, "u_id": 1, "p_id": 102, "qty": 1, "status": "Pending" },
  { "o_id": 1015, "u_id": 3, "p_id": 101, "qty": 2, "status": "Shipped" },
  { "o_id": 1020, "u_id": 5, "p_id": 104, "qty": 4, "status": "Pending" }
]);

db.Payments.insertMany([
  { "pay_id": 29109, "o_id": 1000, "amount": 1000, "status": "Paid", "method": "UPI" },
  { "pay_id": 34522, "o_id": 1005, "amount": 625, "status": "Paid", "method": "Net-banking" },
  { "pay_id": 89231, "o_id": 1010, "amount": 345, "status": "Not-Paid", "method": "Cash" },
  { "pay_id": 56218, "o_id": 1015, "amount": 40, "status": "Paid", "method": "UPI" },
  { "pay_id": 90743, "o_id": 1020, "amount": 200, "status": "Pending", "method": "Card" }
]);

Reading Documents

// View all documents in a collection
Exercise-1> db.Users.find();
[
  {
    _id: ObjectId('67ee0db1d5b35e1b0e6b140b'),
    u_id: 1,
    name: 'Kathir',
    city: 'Madurai'
  },
  {
    _id: ObjectId('67ee0db1d5b35e1b0e6b140c'),
    u_id: 2,
    name: 'Jeeva',
    city: 'Paramakudi'
  },
  {
    _id: ObjectId('67ee0db1d5b35e1b0e6b140d'),
    u_id: 3,
    name: 'Arun',
    city: 'Chennai'
  },
  {
    _id: ObjectId('67ee0db1d5b35e1b0e6b140e'),
    u_id: 4,
    name: 'Mohan',
    city: 'Coimbatore'
  },
  {
    _id: ObjectId('67ee0db1d5b35e1b0e6b140f'),
    u_id: 5,
    name: 'Ravi',
    city: 'Trichy'
  }
]

Finding Specific Documents

// Find by name
Exercise-1> db.Users.find({name:"Kathir"});
[
  {
    _id: ObjectId('67ee0db1d5b35e1b0e6b140b'),
    u_id: 1,
    name: 'Kathir',
    city: 'Madurai'
  }
]

// Find by user ID
Exercise-1> db.Orders.find({u_id:2});
[
  {
    _id: ObjectId('67ee0f9ad5b35e1b0e6b1410'),
    o_id: 1000,
    u_id: 2,
    p_id: 101,
    qty: 3,
    status: 'Pending'
  },
  {
    _id: ObjectId('67ee0f9ad5b35e1b0e6b1411'),
    o_id: 1005,
    u_id: 2,
    p_id: 103,
    qty: 25,
    status: 'Delivered'
  }
]

Update Operations

Updating a Single Document

// Update order status
Exercise-1> db.Orders.updateOne({ o_id: 1000 }, { $set: { status: "Delivered" } });
{
  acknowledged: true,
  insertedId: null,
  matchedCount: 1,
  modifiedCount: 1,
  upsertedCount: 0
}

// Verify update
Exercise-1> db.Orders.find({o_id:1000});
[
  {
    _id: ObjectId('67ee0f9ad5b35e1b0e6b1410'),
    o_id: 1000,
    u_id: 2,
    p_id: 101,
    qty: 3,
    status: 'Delivered'
  }
]

Updating with Increment Operation

// Decrease stock after purchase
Exercise-1> db.Products.updateOne({p_id:103},{$inc: {stock: -25}});
{
  acknowledged: true,
  insertedId: null,
  matchedCount: 1,
  modifiedCount: 1,
  upsertedCount: 0
}

// Verify stock decrease
Exercise-1> db.Products.find({p_id:103});
[
  {
    _id: ObjectId('67ee0e92d5b35e1b0e6b140f'),
    p_id: 103,
    name: 'Carrot',
    price: 25,
    category: 'Vegetables',
    stock: 75
  }
]

Updating Multiple Documents

// Increase all product prices by 100
Exercise-1> db.Products.updateMany({},{$inc:{price:100}});
{
  acknowledged: true,
  insertedId: null,
  matchedCount: 5,
  modifiedCount: 5,
  upsertedCount: 0
}

Replacing an Entire Document

// Replace document with new fields
Exercise-1> db.Users.replaceOne({name:"Kathir"},{name:"Kathir",city:"Paramakudi",age:34});
{
  acknowledged: true,
  insertedId: null,
  matchedCount: 1,
  modifiedCount: 1,
  upsertedCount: 0
}

// Verify replacement
Exercise-1> db.Users.find({name:"Kathir"});
[
  {
    _id: ObjectId('67ee0db1d5b35e1b0e6b140b'),
    name: 'Kathir',
    city: 'Paramakudi',
    age: 34
  }
]

Deletion Operations

Deleting a Single Document

// Delete a user
db.Users.deleteOne({u_id:1});

// Delete an order
db.Orders.deleteOne({o_id: 1005});

Deleting Multiple Documents

// Delete products with price less than 25
Exercise-1> db.Products.deleteMany({price:{$lt:25}});
{ acknowledged: true, deletedCount: 0 }

// Delete all documents in a collection
db.users.deleteMany({})

Search and Filtering

Status-Based Filtering

// Find orders with "Pending" status
Exercise-1> db.Orders.find({status:"Pending"});
[
  {
    _id: ObjectId('67ee0f9ad5b35e1b0e6b1412'),
    o_id: 1010,
    u_id: 1,
    p_id: 2,
    qty: 1,
    status: 'Pending'
  },
  {
    _id: ObjectId('67ee0f9ad5b35e1b0e6b1414'),
    o_id: 1020,
    u_id: 5,
    p_id: 104,
    qty: 4,
    status: 'Pending'
  }
]

Comparison Operators

// Find products with price >= 25
Exercise-1> db.Products.find({price:{$gte:25}});
[
  {
    _id: ObjectId('67ee0e92d5b35e1b0e6b140e'),
    p_id: 102,
    name: 'Headphone',
    price: 500,
    category: 'Electronics',
    stock: 10
  },
  {
    _id: ObjectId('67ee0e92d5b35e1b0e6b140f'),
    p_id: 103,
    name: 'Carrot',
    price: 25,
    category: 'Vegetables',
    stock: 75
  },
  {
    _id: ObjectId('67ee0e92d5b35e1b0e6b1410'),
    p_id: 104,
    name: 'Notebook',
    price: 50,
    category: 'Stationery',
    stock: 30
  },
  {
    _id: ObjectId('67ee0e92d5b35e1b0e6b1411'),
    p_id: 105,
    name: 'Mouse',
    price: 400,
    category: 'Electronics',
    stock: 15
  }
]

// Find products with price between 121 and 500
Exercise-1> db.Products.find({ price: { $gte: 121, $lte: 500 } });
[
  {
    _id: ObjectId('67ee0e92d5b35e1b0e6b140f'),
    p_id: 103,
    name: 'Carrot',
    price: 125,
    category: 'Vegetables',
    stock: 75
  },
  {
    _id: ObjectId('67ee0e92d5b35e1b0e6b1410'),
    p_id: 104,
    name: 'Notebook',
    price: 150,
    category: 'Stationery',
    stock: 30
  },
  {
    _id: ObjectId('67ee0e92d5b35e1b0e6b1411'),
    p_id: 105,
    name: 'Mouse',
    price: 500,
    category: 'Electronics',
    stock: 15
  }
]

Regular Expression Queries

// Find users whose name starts with "K"
Exercise-1> db.Users.find({name:/^K/});
[
  {
    _id: ObjectId('67ee0db1d5b35e1b0e6b140b'),
    u_id: 1,
    name: 'Kathir',
    city: 'Madurai'
  }
]

// Find users whose name ends with "r"
Exercise-1> db.Users.find({name:/r$/});
[
  {
    _id: ObjectId('67ee0db1d5b35e1b0e6b140b'),
    u_id: 1,
    name: 'Kathir',
    city: 'Madurai'
  }
]

// Find users whose city contains "re" (case-insensitive)
Exercise-1> db.Users.find({city:{$regex:"re",$options:"i"}});
[
  {
    _id: ObjectId('67ee0db1d5b35e1b0e6b140e'),
    u_id: 4,
    name: 'Mohan',
    city: 'Coimbatore'
  }
]

// Find users whose name contains "ka" (case-insensitive)
Exercise-1> db.Users.find({name:{$regex:"ka",$options:"i"}});
[
  {
    _id: ObjectId('67ee0db1d5b35e1b0e6b140b'),
    name: 'Kathir',
    city: 'Paramakudi',
    age: 34
  }
]

Inclusion and Exclusion Operators

// Find users whose name is in a list
Exercise-1> db.Users.find({name:{$in:["Kathir","Jeeva","Ganesan"]}});
[
  {
    _id: ObjectId('67ee0db1d5b35e1b0e6b140b'),
    name: 'Kathir',
    city: 'Paramakudi',
    age: 34
  },
  {
    _id: ObjectId('67ee0db1d5b35e1b0e6b140c'),
    u_id: 2,
    name: 'Jeeva',
    city: 'Paramakudi'
  }
]

// Find users whose name is not "Kathir"
Exercise-1> db.Users.find({name:{$ne:"Kathir"}});
[
  {
    _id: ObjectId('67ee0db1d5b35e1b0e6b140c'),
    u_id: 2,
    name: 'Jeeva',
    city: 'Paramakudi'
  },
  {
    _id: ObjectId('67ee0db1d5b35e1b0e6b140d'),
    u_id: 3,
    name: 'Arun',
    city: 'Chennai'
  },
  {
    _id: ObjectId('67ee0db1d5b35e1b0e6b140e'),
    u_id: 4,
    name: 'Mohan',
    city: 'Coimbatore'
  },
  {
    _id: ObjectId('67ee0db1d5b35e1b0e6b140f'),
    u_id: 5,
    name: 'Ravi',
    city: 'Trichy'
  }
]

Projection

// Show only name and city with ID
Exercise-1> db.Users.find({},{name:1,city:1});
[
  {
    _id: ObjectId('67ee0db1d5b35e1b0e6b140b'),
    name: 'Kathir',
    city: 'Madurai'
  },
  {
    _id: ObjectId('67ee0db1d5b35e1b0e6b140c'),
    name: 'Jeeva',
    city: 'Paramakudi'
  },
  {
    _id: ObjectId('67ee0db1d5b35e1b0e6b140d'),
    name: 'Arun',
    city: 'Chennai'
  },
  {
    _id: ObjectId('67ee0db1d5b35e1b0e6b140e'),
    name: 'Mohan',
    city: 'Coimbatore'
  },
  {
    _id: ObjectId('67ee0db1d5b35e1b0e6b140f'),
    name: 'Ravi',
    city: 'Trichy'
  }
]

// Show only name and city, exclude ID
Exercise-1> db.Users.find({},{name:1,city:1,_id:0});
[
  { name: 'Kathir', city: 'Madurai' },
  { name: 'Jeeva', city: 'Paramakudi' },
  { name: 'Arun', city: 'Chennai' },
  { name: 'Mohan', city: 'Coimbatore' },
  { name: 'Ravi', city: 'Trichy' }
]

// Exclude ID when finding users whose name is not "Kathir"
Exercise-1> db.Users.find({name:{$ne:"Kathir"}},{_id:0});
[
  { u_id: 2, name: 'Jeeva', city: 'Paramakudi' },
  { u_id: 3, name: 'Arun', city: 'Chennai' },
  { u_id: 4, name: 'Mohan', city: 'Coimbatore' },
  { u_id: 5, name: 'Ravi', city: 'Trichy' }
]

Existence Checks

// Find users where age is not specified
Exercise-1> db.Users.find({age:{$exists:false}});
[
  {
    _id: ObjectId('67ee0db1d5b35e1b0e6b140c'),
    u_id: 2,
    name: 'Jeeva',
    city: 'Paramakudi'
  },
  {
    _id: ObjectId('67ee0db1d5b35e1b0e6b140d'),
    u_id: 3,
    name: 'Arun',
    city: 'Chennai'
  },
  {
    _id: ObjectId('67ee0db1d5b35e1b0e6b140e'),
    u_id: 4,
    name: 'Mohan',
    city: 'Coimbatore'
  },
  {
    _id: ObjectId('67ee0db1d5b35e1b0e6b140f'),
    u_id: 5,
    name: 'Ravi',
    city: 'Trichy'
  }
]

// Find users where city is not specified
Exercise-1> db.Users.find({city:{$exists:false}});
// (Empty result as all users have city specified)

// Find users where age is specified
Exercise-1> db.Users.find({age:{$exists:true}});
[
  {
    _id: ObjectId('67ee0db1d5b35e1b0e6b140b'),
    name: 'Kathir',
    city: 'Paramakudi',
    age: 34
  }
]

Aggregation Framework

Using $lookup for Joins

// Join order details with user information
Exercise-1> db.Orders.aggregate([
  { 
    $lookup: { 
      from: "Users", 
      localField: "u_id", 
      foreignField: "u_id", 
      as: "user" 
    } 
  }, 
  { $unwind: "$user" }, 
  { 
    $project: { 
      _id: 0, 
      "user.name": 1, 
      p_id: 1, 
      qty: 1, 
      status: 1, 
      "user.city": 1 
    } 
  }
]);
[
  {
    p_id: 101,
    qty: 3,
    status: 'Delivered',
    user: { name: 'Jeeva', city: 'Paramakudi' }
  },
  {
    p_id: 103,
    qty: 25,
    status: 'Delivered',
    user: { name: 'Jeeva', city: 'Paramakudi' }
  },
  {
    p_id: 101,
    qty: 2,
    status: 'Shipped',
    user: { name: 'Arun', city: 'Chennai' }
  },
  {
    p_id: 104,
    qty: 4,
    status: 'Pending',
    user: { name: 'Ravi', city: 'Trichy' }
  }
]

Join with Flattened Fields

// Extract user details to root level
Exercise-1> db.Orders.aggregate([
  {
    $lookup:{
      from:"Users",
      localField:"u_id",
      foreignField:"u_id",
      as:"users"
    }
  },
  {
    $unwind: "$users"
  },
  {
    $project:{
      _id:0,
      name:"$users.name",   // Extract 'name' from 'user' object
      city:"$users.city",
      p_id:1,
      qty:1,
      status:1
    }
  }
]);
[
  {
    p_id: 101,
    qty: 3,
    status: 'Delivered',
    name: 'Jeeva',
    city: 'Paramakudi'
  },
  {
    p_id: 103,
    qty: 25,
    status: 'Delivered',
    name: 'Jeeva',
    city: 'Paramakudi'
  },
  {
    p_id: 101,
    qty: 2,
    status: 'Shipped',
    name: 'Arun',
    city: 'Chennai'
  },
  {
    p_id: 104,
    qty: 4,
    status: 'Pending',
    name: 'Ravi',
    city: 'Trichy'
  }
]

Lookup Without Unwind

// Join without flattening arrays
Exercise-1> db.Orders.aggregate([
  { 
    $lookup: { 
      from: "Users", 
      localField: "u_id", 
      foreignField: "u_id", 
      as: "users" 
    } 
  }, 
  { 
    $project: { 
      _id: 0, 
      name: "$users.name", 
      city: "$users.city", 
      p_id: 1, 
      qty: 1, 
      status: 1 
    } 
  }
]);
[
  {
    p_id: 101,
    qty: 3,
    status: 'Delivered',
    name: [ 'Jeeva' ],
    city: [ 'Paramakudi' ]
  },
  {
    p_id: 103,
    qty: 25,
    status: 'Delivered',
    name: [ 'Jeeva' ],
    city: [ 'Paramakudi' ]
  },
  { p_id: 2, qty: 1, status: 'Pending', name: [], city: [] },
  {
    p_id: 101,
    qty: 2,
    status: 'Shipped',
    name: [ 'Arun' ],
    city: [ 'Chennai' ]
  },
  {
    p_id: 104,
    qty: 4,
    status: 'Pending',
    name: [ 'Ravi' ],
    city: [ 'Trichy' ]
  }
]

Using $group

// Count orders by user
Exercise-1> db.Orders.aggregate([
  {
    $group:{
      _id:"$u_id",
      totalOrders:{$sum:1}
    }
  }
]);
[
  { _id: 3, totalOrders: 1 },
  { _id: 1, totalOrders: 1 },
  { _id: 2, totalOrders: 2 },
  { _id: 5, totalOrders: 1 }
]

Renaming Fields in Aggregation

// Rename _id to userId in group result
Exercise-1> db.Orders.aggregate([
  {
    $group:{
      _id:"$u_id",
      totalOrder:{$sum:1}
    }
  },
  {
    $project:
    {
      userId:"$_id",
      _id:0,
      totalOrder:1
    }
  }
]);
[
  { totalOrder: 1, userId: 1 },
  { totalOrder: 1, userId: 3 },
  { totalOrder: 2, userId: 2 },
  { totalOrder: 1, userId: 5 }
]

Sorting with Aggregation

// Sort orders by quantity in descending order
Exercise-1> db.Orders.aggregate([
  {
    $sort:{qty:-1}
  }
]);
[
  {
    _id: ObjectId('67ee0f9ad5b35e1b0e6b1411'),
    o_id: 1005,
    u_id: 2,
    p_id: 103,
    qty: 25,
    status: 'Delivered'
  },
  {
    _id: ObjectId('67ee0f9ad5b35e1b0e6b1414'),
    o_id: 1020,
    u_id: 5,
    p_id: 104,
    qty: 4,
    status: 'Pending'
  },
  {
    _id: ObjectId('67ee0f9ad5b35e1b0e6b1410'),
    o_id: 1000,
    u_id: 2,
    p_id: 101,
    qty: 3,
    status: 'Delivered'
  },
  {
    _id: ObjectId('67ee0f9ad5b35e1b0e6b1413'),
    o_id: 1015,
    u_id: 3,
    p_id: 101,
    qty: 2,
    status: 'Shipped'
  },
  {
    _id: ObjectId('67ee0f9ad5b35e1b0e6b1412'),
    o_id: 1010,
    u_id: 1,
    p_id: 2,
    qty: 1,
    status: 'Pending'
  }
]

// Sort and project specific fields
Exercise-1> db.Orders.aggregate([
  {
    $sort:{qty:-1}
  },
  {
    $project:
    {
      qty:1,
      o_id:1,
      _id:0
    }
  }
]);
[
  { o_id: 1005, qty: 25 },
  { o_id: 1020, qty: 4 },
  { o_id: 1000, qty: 3 },
  { o_id: 1015, qty: 2 },
  { o_id: 1010, qty: 1 }
]

// Sort by quantity ascending
Exercise-1> db.Orders.aggregate([
  { 
    $sort: { qty: 1 } 
  }, 
  { 
    $project: { 
      qty: 1, 
      o_id: 1, 
      _id: 0 
    } 
  }
]);
[
  { o_id: 1010, qty: 1 },
  { o_id: 1015, qty: 2 },
  { o_id: 1000, qty: 3 },
  { o_id: 1020, qty: 4 },
  { o_id: 1005, qty: 25 }
]

Filter and Aggregation

// Calculate total sales for delivered orders
Exercise-1> db.Orders.aggregate([
  {
    $match:{status:"Delivered"}
  },
  {
    $group:{
      _id:null,
      totalSales:{$sum:"$qty"}
    }
  }
]);
[ { _id: null, totalSales: 28 } ]

Complex Aggregation Operations

// Calculate total revenue from each product
Exercise-1> db.Orders.aggregate([
  { 
    $lookup: { 
      from: "Products", 
      localField: "p_id", 
      foreignField: "p_id", 
      as: "product_details" 
    } 
  }, 
  { 
    $unwind: "$product_details" 
  }, 
  { 
    $group: { 
      _id: "$p_id", 
      totalRevenue: { 
        $sum: { 
          $multiply: ["$qty", "$product_details.price"] 
        } 
      } 
    } 
  }, 
  { 
    $sort: { 
      totalRevenue: -1 
    } 
  }
]);
[
  { _id: 103, totalRevenue: 3125 },
  { _id: 104, totalRevenue: 600 },
  { _id: 101, totalRevenue: 600 }
]

Import and Export Operations

Exporting Collections to JSON

# Export to current directory
kathir@KathirLinux:~$ mongoexport --db=Exercise-1 --collection=Users --out=Users.json --jsonArray
2025-04-03T22:37:56.295+0530	connected to: mongodb://localhost/
2025-04-03T22:37:56.305+0530	exported 5 records

# Export to Downloads folder
mongoexport --db=Exercise-1 --collection=Users --out=~/Downloads/Users.json --jsonArray

Importing Collections from JSON

# First drop the collection
Exercise-1> db.Users.drop();
true
Exercise-1> db.Users.find();
# (Empty result)

# Import from JSON file
kathir@KathirLinux:~$ mongoimport --db=Exercise-1 --collection=Users --file=Users.json --jsonArray;
2025-04-03T22:43:56.480+0530	connected to: mongodb://localhost/
2025-04-03T22:43:56.561+0530	5 document(s) importe

Key Aggregation Concepts

  • $lookup: Performs a left outer join with another collection
  • $unwind: Flattens array fields into separate documents
  • $group: Groups documents by specified fields and applies aggregation operations
  • $project: Selects, renames, or modifies fields in documents
  • $match: Filters documents similar to the find() method
  • $sort: Sorts documents by specified fields

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