How to Find MongoDB Records Where Array Field is not Empty?

In MongoDB, efficient querying is essential for retrieving relevant data from collections. One common requirement in database management is to find documents where specific array fields are not empty. This task is particularly relevant in scenarios where data integrity is crucial.

In this article, we will learn about How to find MongoDB records where the array field is not empty with the help of the $exists operator along with the understanding of various examples and so on.

How to Find MongoDB Records Where Array Field is not Empty?

When working with MongoDB, it is necessary to retrieve documents where specific array fields are not empty. To solve this, MongoDB provides querying operators like $exists and $ne to efficiently filter documents based on MongoDB records where array field is not empty.

We can use the following MongoDB query syntax:

db.collectionName.find({ "arrayFieldName": { $exists: true, $not: { $size: 0 } } })

• db.collectionName: This refers to the MongoDB database and the specific collection within that database where the documents are stored.
• .find(): It is used to query documents from a collection.
• $exists: true, which verifies the presence of the specified field in the document.
• $not: { $size: 0 }, ensuring that the size of the specified field is greater than 0, thus confirming that the array field isn’t empty.

Let’s set up an Environment:

To understand How to Find MongoDB records where array field is not empty we need a collection and some documents on which we will perform various operations and queries.

Here we will consider a collection called arrayFieldIsNotEmptyDemo which contains information like StudentName and StudentTechnicalSubject of the arrayFieldIsNotEmptyDemo in various documents.

 db.arrayFieldIsNotEmptyDemo.insertMany([     
{ "StudentName": [], "StudentTechnicalSubject": ["Java", "python"]},     
{ "StudentName": "Mike",   "StudentTechnicalSubject": []},     
{   "StudentName": "Sam",  "StudentTechnicalSubject": ["MongoDB"]},     
{"StudentName": "Carol",  "StudentTechnicalSubject": [] },     
{ "StudentName": [], "StudentTechnicalSubject": ["MySQL", "SQL Server"] } 
]);

Output:

Examples of Find MongoDB Records Where Array Field is Not Empty

Example 1:

Let’s Retrieve documents from the “arrayFieldIsNotEmptyDemo” collection where the “StudentTechnicalSubject” array field is not empty.

// Finding records where the array field is not empty
> db.arrayFieldIsNotEmptyDemo.find({ StudentTechnicalSubject: { $exists: true, $ne: [] } }).pretty();

Output:

Finding records where array field is not empty

Explanation: In the above output, we finded MongoDB records where array field is not empty in the array field of StudentTechnicalSubject easily.

Example 2:

Lets Retrieve documents from the “arrayFieldIsNotEmptyDemo” collection where the “StudentName” array field is not empty.

// Finding records where the array field is not empty
db.arrayFieldIsNotEmptyDemo.find({ StudentName: { $exists: true, $ne: [] } }).pretty();

Output:

Finding records where array field is not empty

Explanation: In the above output, we finded MongoDB records where array field is not empty in the array field of StudentName easily.

Conclusion

Overall, In MongoDB, querying for documents where an array field is not empty is straightforward using the $exists and $ne operators. By understanding these querying techniques, you can efficiently retrieve the desired data from your MongoDB collections.