The aggregate operator in MongoDB is used to process data records and return computed results. It can perform various operations on data like grouping it based on certain fields or doing calculations on it, etc.
To use the aggregate operator, follow these steps:
1. Choose the collection you wish to perform the aggregation on.
1. Call the aggregate method on your selected collection.
1. Pass in an array of your aggregation pipeline stages. Each stage in the pipeline processes data records and supplies the result to the next pipeline stage.
Here is a basic example of how to use the aggregate operator in MongoDB:
```
db.collection.aggregate([
{ $match: { status: “A” } },
{ $group: { _id: “$cust_id”, total: { $sum: “$amount” } } }
])
```
- `$match` is used for filtering data. It works like the find() method. In the above example, it filters out the documents where status is ‘A’.
- `$group` is used to group data. In the given example, fields are grouped based on the “cust_id” field, and for each distinct cust_id, it calculates a sum of the “amount” and store it in “total”.
Note: The above code is written in the MongoDB shell JavaScript syntax. The syntax will be different if used with any MongoDB driver. Also, the aggregate operator is provided by MongoDB, not a driver, therefore it’s available in all MongoDB drivers with almost exactly the same syntax.
