MongoDB - Logical Query Operators

In MongoDB, logical query operators combine multiple conditions within a single query. They enable complex filtering and allow more flexible and precise data retrieval. It is commonly used for advanced searches, conditional filtering, and data analysis scenarios.

Here is a detailed explanation of the most commonly used logical query operators in MongoDB. It Joins query clauses with a logical OR. Returns documents that match any of the conditions.

Examples of Logical Query Operators

Let’s go deeper into how each operator works with examples from a sample MongoDB collection. In the following examples, we are working with:

• Database: GeeksforGeeks
• Collection: contributor
• Document: three documents that contain the details of the contributors in the form of field-value pairs.

Example 1: Matching values using $and operator

The $and operator is used to combine multiple conditions, where all conditions must be met. In this example, we are retrieving only those employee’s documents whose branch is CSE and joiningYear is 2018.

Query:

db.contributor.find({$and: [{branch: "CSE"}, {joiningYear: 2018}]}).pretty()

Output

Explanation: This query will only return documents where both conditions are true: the branch is "CSE" and the joiningYear is 2018.

Example 2: Matching values using $nor operator

The $nor operator is the opposite of $or. It retrieves documents where none of the specified conditions are met. In this example, we are retrieving only those employee’s documents whose salary is not 3000 and whose branch is not ECE.

Query:

 db.contributor.find({$nor: [{salary: 3000}, {branch: "ECE"}]}).pretty()

Output

Explanation: This query will return documents where neither of the conditions (salary: 3000 or branch: "ECE") is true.

Example 3: Matching values using $or operator

The $or operator combines multiple conditions, where at least one of the conditions must be true. In this example, we are retrieving only those employee’s documents whose branch is ECE or joiningYear is 2017.

Query:

db.contributor.find({$or: [{branch: "ECE"}, {joiningYear: 2017}]}).pretty()

Output

Explanation:

• This query returns documents where either the branch is "ECE" or the joiningYear is 2017.
• If either of the conditions is true, the document will be returned.

Example 4: Matching values using $not operator

The $not operator is used to negate the effect of a query expression. In this example, we are retrieving only those employee’s documents whose salary is not greater than 2000.

Query:

db.contributor.find({salary: {$not: {$gt: 2000}}}).pretty()

Output

Explanation:

• This query returns documents where the salary is less than or equal to 2000.
• The $gt operator checks if the value is greater than 2000, and $not negates this condition.