In this Tutorial, we will learn how the MongoDB potent tool Aggregation Framework works, allowing us to perform some complex analysis including manipulations in MongoDB Collections, where it works by grouping and transforming the documents into a collection which all is done on the basis of some defined stages that we will discuss here one by one
Aggregation Framework
Here we will discuss all the steps of the aggregation framework.
Step 1. It is the stage that could be optional as in this step we simply pipeline using $match step where we filter the documents in the collection on the basis of pre defined criteria. This step help in reducing the number of documents that we are going to aggregate and remove which are not required.
Step 2. It is the step of $group which is used for grouping the documents on the basis of one or more than one field. And after grouping, we can perform any number of calculations on the data we grouped for example making sum, average, count, Minimum, maximum, etc.
Step 3. It is the $project step where we transform the data and select only the fields we need or we can also add the fields which we want on output we might require.
Step 4. As per the next step, we have $sort where we can sort the data of the group or the group itself in any form like ascending or descending.
Step 5. In this step, we $limit and $skip which is used for limiting the number of documents or skipping the documents that we want to skip or we do not want to continue with.
Step 6. In this step, we $unwind where we create a new document for each array element created.
Step 7. It is nothing but $Lookup which is used for linking or joining the collections to each other.
For an example of the same follow the code given below where we have taken an example to elaborate and understand it in a better way and learn more.
db. sales. aggregate([
{ $group: {
_id: "$product",
totalRevenue: { $sum: { $multiply: [ "$price", "$quantity" ] } }
} }
])
It is simple aggregation and many other stages are also available that we could perform for some complex data analysis and transformations.
To learn more about How The MongoDB Aggregation Framework visit: The aggregate framework in MongoDB.
To learn more about MongoDB solutions and tutorials for the problems faced in MongoDB visit: MongoDB Problems And Tutorials.
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