MongoDB $strcasecmp Operator

$strcasecmp performs case-insensitive alphabetical comparison between two strings in the aggregation pipeline and returns a numeric value that indicates their relative order or equality.

• Compares two strings without considering letter case.
• Returns 0 when both strings are equal ignoring case.
• Returns 1 when the first string is lexicographically greater.
• Returns -1 when the first string is lexicographically smaller.
• Commonly used in $project, $addFields, and $expr-based filters for flexible string matching.

Syntax

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

• <expression1>: The first string or expression to compare.
• <expression2>: The second string or expression to compare.
• The $strcasecmp operator resolves both expressions to strings, performs the case-insensitive comparison, and returns the result.

Examples of MongoDB $strcasecmp Operator

Examples of the $strcasecmp operator. In the following examples, we are working with:

• Database: GeeksforGeeks
• Collection: employee
• Document: Three documents that contain the details of the employees in the form of field-value pairs.

Example 1: Using $strcasecmp Operator

Compare the value of the department field of all the documents present in employee collection with the "development" string using $strcasecmp operator. 

db.employee.aggregate([
  {
    $project: {
      "name.first": 1,
      _id: 0,
      result: { $strcasecmp: ["$department", "development"] }
    }
  }
])

Output:

• Compares each document’s department with "development" in a case-insensitive manner.
• Outputs 0 when both strings are equal (ignoring case).
• Outputs 1 when department is lexicographically greater.

Example 2: Using $strcasecmp Operator in the Embedded Document

Compare the value of the name.first field of all the documents present in employee collection with the "Lucas" string using $strcasecmp operator. 

db.employee.aggregate([
  {
    $project: {
      result: { $strcasecmp: ["$name.first", "Lucas"] }
    }
  }
])

Output:

• Outputs 0 when both strings are equal (ignoring case).
• Outputs 1 when name.first is lexicographically greater.
• Outputs -1 when name.first is lexicographically smaller.

$strcasecmp in Aggregation Pipelines

$strcasecmp enables case-insensitive, lexicographical comparison of strings within MongoDB’s aggregation pipeline.

• Performs case-insensitive comparison of two strings in aggregation stages.
• Returns 1 if the first string is greater, 0 if both strings are equal, and -1 if the first string is smaller.
• Useful when simple string comparison is needed without case sensitivity.
• Comparison behavior depends on MongoDB’s collation settings; for language-specific rules, use collation instead of relying solely on $strcasecmp.

Common Use Cases for $strcasecmp

Here are some common use cases:

• User Input Validation: Match names, emails, or other fields without case sensitivity.
• Case-Insensitive Sorting: Sort strings like names or emails regardless of letter case.
• Filtering Records: Find records by string fields (e.g., department) ignoring case.
• Data Deduplication: Detect duplicates that differ only by letter case.
• Flexible Matching: Normalize comparisons where case variation is irrelevant.