Your Complete Guide to MongoDB: Part Two (Advanced Query Filtering)

Previous lessons

• Part one

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Table of contents

• Download and import restaurants data set
• Read queries

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Download and import restaurants collection

• Open mongodb compass

• Connect to your local host

• Open mongodb compass
  

• Create new database called shops

• Click Add Data
• Import JSON file

• Select the downloaded JSON from my github repository

• Open mongosh terminal

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Use shops database.

 use shops

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Read Queries

• Comparison:
  • $eq:
  • $elemMatch:
  • $ne:
  • $gt:
  • $gte:
  • $lt:
  • $lte:
  • $in:
  • $nin:
• Logical:
  • $and:
  • $or:
  • $nor:
  • $not:
• Evaluation:
  • $regex:
  • $text:
  • $where:

---

$eq Stands for Equal

$eq is an operator used to match documents where the value of a field is equal to a specified value.

find documents with rating equal to 4.

db.restaurants.find( 
  {
    rating:{
      $eq: 4
    }
  }
)
//or you can just match directly without using $eq
db.restaurants.find( 
  {
    rating: 4
  }
)

---

$elemMatch vs matching directly

db.restaurants.find(
  {
        "grades": {
          $elemMatch:{
           grade: "A",
            score:6
            grade: "A"
          }
        }
      }
)

db.restaurants.find(
  {
        "grades.grade": "A"
        "grades.score": 6
   }
)

matching directly like This means that the "grades" array may contain other elements besides the one with "grade" equal to "A" so it will return this document.

---

$elemMatch will make sure that the element inside grades array must have one element having score of 6 and grade of A so it will not return this document.

---

$ne

$ne stands for Not Equal.

find restaurants with grades not equal to "A".

db.restaurants.find(
{
      grades: {
        $elemMatch: {
          grade: {
            $ne: "A"
          }
        }
      }
    }
)

---

$gt

$gt Stands For Greater Than.

find restaurants with rating greater than 3.

db.restaurants.find({ rating: { $gt: 3} })

---

$gte

$gte Stands For Greater Than.

find restaurants with rating greater than or equal 4.

db.restaurants.find({ rating: { $gte: 4} })

---

$lt

Stands for Less Than.

find restaurants with rating lower than 2.

db.restaurants.find({ shopRank: { $lt: 2} })

---

$lte

Stands for Less Than Or Equal.

find restaurants with rating lower than or equal 5.

db.restaurants.find({ rating: { $lte: 5} })

---

$in

Find restaurants in these three cuisine categories "Bakery", "Irish", "American" 1, 3, 5.

db.restaurants.find(
{
      cuisine: {
        $in: ["American", "Irish", "Bakery"]
      }
    }
)

---

$nin

$nin stands for Not In.

Find restaurants not in these three shop ranks 1, 3, 5 .

db.restaurants.find(
{
      cuisine: {
        $nin: ["American", "Irish", "Bakery"]
      }
    }
)

---

$and

$and is a logical operator used within queries to specify multiple conditions

$and returns all documents that meets all conditions specified

Find restaurants with with cuisine equal to "American" and rating higher than 3.

db.restaurants.find( 
  {
      $and: [
        { cuisine: "Irish" },
        { rating: { $gt: 1 } }
      ]
  }
)

---

$or

$or is another logical operator used within queries to specify multiple conditions but unlike $and $or requires at least one condition to be met

Find restaurants with with cuisine equal to "American" or rating higher than 3.

db.restaurants.find( 
  {
      $or: [
        { cuisine: "Irish" },
        { rating: { $gt: 1 } }
      ]
  }
)

---

$nor

$nor is the exact opposite or $or it finds documents that doesn't meet any of the conditions .

Find restaurants with with cuisine not equal to "American" or rating not higher than 3.

db.restaurants.find( 
  {
      $or: [
        { cuisine: "Irish" },
        { rating: { $gt: 1 } }
      ]
  }
)

---

$not

$not is the exact opposite or $eq.

Find restaurants with with cuisine not equal to "American" or rating not higher than 3.

db.restaurants.find( 
  {
      cuisine: {
         $not: { $eq: "American" }
     }
  }
)

---

$regex

$regex operator is used to perform regular expression-based pattern matching within queries. It allows you to search for documents where a specified field matches a regular expression pattern.

Find restaurants where the name starts with mor and case insensitive.

db.restaurants.find( 
  {
      title: {
        $regex: /mor/,
        $options: "i" // case insensitive option
     } 
  }
)

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$text and $search

$text and $search operator is used to perform a full-text search on text fields within a collection. It's specifically designed for searching text content efficiently.

Find restaurants where the name starts with morris.

db.restaurants.find( 
  {
      $text: { $search: "morris" }
  }
)

---

$where

$where allows you to write javascript code directly into the query.

Find restaurants where the rating divided by two is still higher that 1.5 .

db.restaurants.find( 
  {
      $where: function () {
        return this.rating / 2  > 1.5;
      }
  }
)

---

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Next parts

• Part three (coming soon)

Comments

[b']

thx

[Abdelhakim mohamed]

Hope you liked it