Find a value in lowercase from a MongoDB collection with documents

To find a value in lowercase from a MongoDB collection, use the toLowerCase() method in JavaScript when constructing your query. This allows you to search for documents where a field matches a specific value in lowercase format.

Syntax

db.collection.find({"fieldName": "VALUE".toLowerCase()});

Sample Data

Let us create a collection with documents containing subject names in different cases ?

db.demo172.insertMany([
    {"SubjectName": "MySQL"},
    {"SubjectName": "mongodb"},
    {"SubjectName": "MongoDB"}
]);

{
    "acknowledged": true,
    "insertedIds": [
        ObjectId("5e3838ce9e4f06af551997e1"),
        ObjectId("5e3838d69e4f06af551997e2"),
        ObjectId("5e3838db9e4f06af551997e3")
    ]
}

Display all documents from the collection ?

db.demo172.find();

{ "_id": ObjectId("5e3838ce9e4f06af551997e1"), "SubjectName": "MySQL" }
{ "_id": ObjectId("5e3838d69e4f06af551997e2"), "SubjectName": "mongodb" }
{ "_id": ObjectId("5e3838db9e4f06af551997e3"), "SubjectName": "MongoDB" }

Example: Find Document with Lowercase Value

Find the document where SubjectName matches "mongodb" in lowercase ?

db.demo172.find({"SubjectName": "MONGODB".toLowerCase()});

{ "_id": ObjectId("5e3838d69e4f06af551997e2"), "SubjectName": "mongodb" }

Key Points

• The toLowerCase() method converts the search string to lowercase before matching.
• This approach only finds documents with exact lowercase matches, not case-insensitive searches.
• For true case-insensitive searches, use regular expressions with the i flag instead.

Conclusion

Use JavaScript's toLowerCase() method within your MongoDB query to find documents with exact lowercase field values. This technique is useful when you need to match specific lowercase formatted data in your collection.