Updated March 8, 2023
Definition of MongoDB not null
MongoDB provides different functionality to the user, the MongoDB not null is one of the functionalities that is provided by the MongoDB. Basically not null is used to avoid the null value during the insertion operation. During the insert operation, we can insert the null values into the collection that means the document contains the null value. With “not null” constraint we can implement the different methods as per our requirement. We can also use the MongoDB comparison operator with “not null” constraint as per our requirement. When we need to display the not null value at that time we need the $exists method.
Syntax:
db.specified collection name.find({specified field name: {“comparison operator” or ”Boolean value ”}} )
Explanation
In the above syntax, we use the find method to implement the not null constraint with different parameters as follows.
- specified collection name: Specified collection name means the actual name of the collection that we already created.
Find: find is a method to search the string. - specified field name: specified field name means a field name that we need to display without null.
After that, we need to use either a comparison operator or Boolean operator as per our requirement.
How not null works in MongoDB?
Now let’s see how not null works in MongoDB as follows.
In the event that we make an association between table and assortment, we see likenesses between lines – reports and sections – fields. The greatest contrast is that each archive from the same assortment can contain altogether different arrangements of fields. So the field can contain invalid, yet it might likewise not be there. Now and then, we need to separate between those. The method of doing checks additionally relies upon the utilization and what would you like to accomplish.
Basically “not null” constraint is used to display the document without null from the collection as per our requirement means as per our requirement we can choose any field name with a different comparison operator and Boolean operator. Basically, we can use the $exists a method to implement the not null in MongoDB. When <boolean> is valid, $exists coordinates with the records that contain the field, including reports where the field esteem is invalid. In case <boolean> is bogus, the question returns just the records that don’t contain the field.
First, try to understand what the operator is. MongoDB provides different kinds of operators such as comparison, logical, element array and bitwise, etc. But we commonly used comparison operators among the different operators. Again we have different types of comparison operators such as eq, gt, lt, and gte, etc, and this operator we can use as per our requirement.
Normally the “not equal” operator is used to compare the specified value with all documents from the collection and if it finds any matching document from the collection then it displays all documents from the collection.
The working of the “not equal” operator is simple; we just need to mention the specified field name with the specified value that we want. The specified field name and specified value depend on the user. At the time of execution, it compares all specified values with all documents from the collection and if the value of the document is not equal to the specified value then it displays specified records.
Examples
Now let’s see different examples of not null in MongoDB for better understanding as follows.
First, we need to create the new collection but before that, we need to create the new database by using the following statement as follows. First, we created a sample database by using the following statement as follows.
use sample
Explanation
In the above statement, we use the command to create the new database, here we successfully created a sample database and we use it. The end result or we can say the output of the above statement we illustrated by using the following screenshot as follows.
After successful creation of the database, we need to create the collection by using the following statement as follows.
db.createCollection(“student_sample”)
Explanation
In the above statement, we use createCollection command to create the new collection; here we created a new collection name as a student_sample as shown. The end result or we can say the output of the above statement we illustrated by using the following screenshot as follows.
Now we have a new collection, so now we need to insert the different document into the newly created collection that is student_sample with a null field so we can get the result. For insertion of the document, we can use the following statement as follows.
db.student_sample.insert({ name: "Johan", dept: "IT", marks: 75, dbsm:56})
db.student_sample.insert({ name: "Sameer", dept: "comp", marks: 12, dbsm:null})
db.student_sample.insert({ name: "pooja", dept: "comp", marks: 45, dbsm:null})
db.student_sample.insert({ name: "Rohit" dept: "mech", marks: 71, dbsm:87})
db.student_sample.insert({ name: "Sachin", dept: "IT", marks: 98, dbsm:null})
Explanation
By using the above statement we insert a document into the student_sample collection, in which we insert names of students, department of the student, and dbsm marks with null field as shown. Now we can see all documents from the collection by using the following statement as follows.
db.student_sample.find()
Explanation
The end result or we can say the output of the above statement we illustrated by using the following screenshot as follows.
Suppose we need to display the not null field from the student_sample collection then we can use the following statement as follows.
db.student_sample.find({"dbsm": {"$ne": null}});
Explanation
In the above example, we try to implement them not null, here we use the find method with the $ne comparison operator as shown. The end result or we can say the output of the above statement we illustrated by using the following screenshot as follows.
The same output we can see in a structured way by using the following statement as follows.
db.student_sample.find().pretty();
Explanation
The end result or we can say the output of the above statement we illustrated by using the following screenshot as follows.
So in this way, we can implement the not null with different methods such as $exists, find, etc in MongoDB.
Conclusion
We hope from this article you learn more about MongoDB not null. From the above article, we have learned the basic syntax of the not null and we also see different examples of the not null. From this article, we learned how and when we use MongoDB not null.
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