Introduction to MongoDB $strcasecmp Operator

The $strcasecmp operator is an aggregation operator used for string comparison in MongoDB. It can be used to conveniently compare two strings for equality, regardless of case.

Syntax

The syntax of the $strcasecmp operator is as follows:

{ $strcasecmp: [ <string expression1>, <string expression2> ] }

• <string expression1>: A string expression representing the first string to be compared.
• <string expression2>: A string expression representing the second string to be compared.

Use cases

In MongoDB, the $strcasecmp operator can be used to compare strings for equality, regardless of case. For example, if a collection has a field that stores the email address of users, we can use the $strcasecmp operator to check if a specified email address has already been registered.

Examples

Example 1

Let’s use the following data as an example:

{ name: 'Alice', email: '[email protected]' }
{ name: 'Bob', email: '[email protected]' }
{ name: 'Charlie', email: '[email protected]' }

Now, we want to find the user with the email address [email protected]. We can use the following aggregation pipeline:

db.collection.aggregate([
  {
    $match: {
      $expr: { $eq: [{ $strcasecmp: ["$email", "[email protected]"] }, 0] }
    }
  }
])

In the above aggregation pipeline, the $match operator is used to filter out users with the email address [email protected]. The $expr operator is used to evaluate the expression, and the $eq operator is used to check if the result of the $strcasecmp operator is equal to 0.

After running the above aggregation pipeline, we get the following result:

{ name: 'Bob', email: '[email protected]' }

Example 2

Let’s use the following data as another example:

{ name: 'charlie', age: 25 }
{ name: 'bob', age: 30 }
{ name: 'Alice', age: 28 }

Now, we want to sort the documents in alphabetical order by name. We can use the following aggregation pipeline:

db.collection.aggregate([{ $sort: { $strcasecmp: ["$name", "asc"] } }])

In the above aggregation pipeline, the $sort operator is used to sort the documents in alphabetical order by the name field using the $strcasecmp operator.

After running the above aggregation pipeline, we get the following result:

{ name: 'Alice', age: 28 }
{ name: 'bob', age: 30 }
{ name: 'charlie', age: 25 }

Conclusion

The $strcasecmp operator is an aggregation operator used for string comparison in MongoDB. It can be used to conveniently compare two strings for equality, regardless of case. In practical use cases, we can use the $strcasecmp operator to achieve different functions, such as string equality comparison, string sorting, and so on, based on specific requirements. When using the $strcasecmp operator, it is important to pay attention to its syntax and parameter types to ensure that the correct expressions and parameters are used. Additionally, to improve performance, we can use the $strcasecmp operator in combination with other operators to reduce query time and resource consumption.