$push: This operator is used to return the expression of array values from each group. $mergeObjects: This operator is used to return the documents which was combined by using input document. $min: This operator is used to return the lowest value from each group. $max: This operator is used to return the highest value from each group. $last: This operator is used to return the each group first document using $group operator. $first: This operator is used to return the each group first document using $group operator. This operator ignores the non-numeric values from the collections. $avg: This operator is used to return the average of all the numeric fields using $group operator. The order of this operator array elements is undefined. $addToSet: This operator is used to return the each group array unique expression value using $group operator. $sum: This operator is used to return the sum of all the numeric fields using $group operator. We are using below operator to group by multiple fields. We are using group method and aggregation operation to use group by in MongoDB. Field: This is defined as field name which we are using with group by in MongoDB. By using accumulator with the expression is accepting the valid expression.While using group by in MongoDB it is must to be use any one accumulator by using group by. Accumulator: We are using the accumulator operator with group operator in MongoDB. Expression with group by is accepting the valid expression. Expression: This is defined as expression which we have using with the group by in MongoDB. We can specify the id value with null value for calculating the accumulated value from the all input values. _id: This field is mandatory while using aggregation with group operator. Group by is not order the result documents. The output of this aggregation is _id field which contains the group by key of distinct records. $group: This is defined as using accumulator and the expression we have retrieving the grouped data from the collection. 
) Parametersīelow is the parameter description syntax of group by in MongoDB: The following documents are inserted into the person collections > db.person.Hadoop, Data Science, Statistics & others In this example, we apply multiple conditions to the documents using the find() method and return documents as per the condition. Let’s understand with the help of an example: when we use the find() method to return a pointer on the selected documents and returns one by one. Here, the cursor indicates a pointer that points to a document. The find() method is used to select the documents from a collection and return a cursor to the selected documents.
In MongoDB, we can apply the multiple conditions using the find() method and retrieve only those documents that match our documents. Read: Pros and cons of MongoDB MongoDB find multiple conditions match You can use the $or operator and retrieve the documents according to the condition. We have got the result successfully as per the given condition.
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Now, See the execution of the above code in the MongoDB shell: The or operator retrieves all those documents that match at least one of the given expressions. Here, we apply the $or operation and show only those documents where age is greater than 25 and gender is Female. The following documents are inserted into the student collection: > db.student.insertMany([Īfter inserting these documents into the collection, we apply $or operator and find only condition specified documents. "award" : "National Medal of Technology",Īfter inserting the documents into the collection, we apply the find() method to retrieve the documents of the collection. "by" : "Data Processing Management Association"
"award" : "Computer Sciences Man of the Year", The following documents are inserted into the data collection: > db.data.insertMany([
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