Regex to ignore a specific character in MongoDB?

To ignore a specific character in MongoDB, use regular expressions with either the $not operator or character negation patterns. These approaches filter out documents containing the unwanted character.

Syntax

// Method 1: Using character negation
db.collection.find({field: /^[^CHARACTER]*$/});

// Method 2: Using $not operator
db.collection.find({field: {$not: /CHARACTER/}});

Sample Data

db.regexDemo.insertMany([
    {"CustomerId": "Customer#1234", "CustomerName": "Chris"},
    {"CustomerId": "Customer5678", "CustomerName": "Robert"},
    {"CustomerId": "Customer#777", "CustomerName": "Carol"},
    {"CustomerId": "Customer777", "CustomerName": "David"}
]);

{
    "acknowledged": true,
    "insertedIds": [
        ObjectId("5cc7428f8f9e6ff3eb0ce436"),
        ObjectId("5cc7429e8f9e6ff3eb0ce437"),
        ObjectId("5cc742ae8f9e6ff3eb0ce438"),
        ObjectId("5cc742bc8f9e6ff3eb0ce439")
    ]
}

Method 1: Using Character Negation

Find all documents where CustomerId does not contain the # character ?

db.regexDemo.find({CustomerId: /^[^#]*$/});

{
    "_id": ObjectId("5cc7429e8f9e6ff3eb0ce437"),
    "CustomerId": "Customer5678",
    "CustomerName": "Robert"
}
{
    "_id": ObjectId("5cc742bc8f9e6ff3eb0ce439"),
    "CustomerId": "Customer777",
    "CustomerName": "David"
}

Method 2: Using $not Operator

Alternative approach using the $not operator to exclude documents containing # ?

db.regexDemo.find({CustomerId: {$not: /#/}});

{
    "_id": ObjectId("5cc7429e8f9e6ff3eb0ce437"),
    "CustomerId": "Customer5678",
    "CustomerName": "Robert"
}
{
    "_id": ObjectId("5cc742bc8f9e6ff3eb0ce439"),
    "CustomerId": "Customer777",
    "CustomerName": "David"
}

Key Differences

• /^[^#]*$/ matches strings that contain only characters other than #
• {$not: /#/} excludes any string that contains the # character anywhere
• Both methods produce the same result for this use case

Conclusion

Use regex patterns with $not operator or character negation [^CHARACTER] to filter out documents containing specific characters. The $not approach is more readable and straightforward for simple character exclusions.