Get distinct first word from a string with MongoDB?

To get distinct first words from a string field in MongoDB, use the distinct() method combined with JavaScript's map() and split() functions to extract and return the first word from each string.

Syntax

db.collection.distinct("fieldName", query).map(function(str) {
    return str.split(" ")[0];
});

Sample Data

db.distinctFirstWordDemo.insertMany([
    {
        "_id": 100,
        "StudentName": "John",
        "StudentFeature": "John is a good player",
        "Subject": "MongoDB"
    },
    {
        "_id": 101,
        "StudentName": "Carol",
        "StudentFeature": "Carol is not a good player",
        "Subject": "MongoDB"
    }
]);

{
    "acknowledged": true,
    "insertedIds": {
        "0": 100,
        "1": 101
    }
}

Display All Documents

db.distinctFirstWordDemo.find();

{
    "_id": 100,
    "StudentName": "John",
    "StudentFeature": "John is a good player",
    "Subject": "MongoDB"
}
{
    "_id": 101,
    "StudentName": "Carol",
    "StudentFeature": "Carol is not a good player",
    "Subject": "MongoDB"
}

Example: Extract Distinct First Words

student = db.distinctFirstWordDemo.distinct("StudentFeature", {"Subject": "MongoDB"}).map(function(st) {
    return st.split(" ")[0];
});

printjson(student);

[ "John", "Carol" ]

How It Works

• distinct("StudentFeature", {"Subject": "MongoDB"}) gets all unique values from the StudentFeature field where Subject is "MongoDB"
• map() applies a function to each string in the result array
• split(" ")[0] splits each string by spaces and returns the first element (index 0)

Conclusion

Use MongoDB's distinct() method with JavaScript's map() and split() functions to efficiently extract distinct first words from string fields. This approach combines MongoDB's query capabilities with client-side string processing.