How to Find MongoDB Records Where Array Field is not Empty?
Last Updated :
31 Jul, 2024
In MongoDB, retrieving documents where specific array fields are not empty. This is useful in scenarios where the presence of data within an array is crucial for filtering results. MongoDB provides several operators, such as $exists
and $ne
to facilitate the querying of documents based on the contents of array fields.
In this article, we will learn How to find MongoDB records where the array field is not empty with the help of the $exists operator 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 the 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 emptyExplanation: 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 emptyExplanation: In the above output, we finded MongoDB records where array field is not empty in the array field of StudentName easily.
Conclusion
Overall, Using MongoDB's querying capabilities, specifically the $exists
and $ne
operators, you can efficiently filter documents based on whether an array field is empty or not. This functionality is crucial for ensuring data completeness and correctness in various applications. By understanding and applying these queries, you can manage and manipulate your data more effectively.
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