# Writing Your First Aggregation

Aggregations refers to when you group a collection by a certain field and then take a metric when it is grouped. 

An example of an aggregation query can be found as below:

```
{
    "groupby" : [
        {"name": <alias>, 
        "field": <field in the collection>, "agg": "category"},
        {"name": <alias>, 
        "field": <another groupby field in the collection>, 
        "agg": "numeric"}
    ],
    "metrics" : [
        {"name": <alias>, 
        "field": <numeric field in the collection>, 
        "agg": "avg"}
        {
        "name": <alias>, 
        "field": <another numeric field in the collection>, 
        "agg": "max"}
    ]
}

```

The available groupby types are:

* category (groupby a field that is a category)
* numeric (groupby a field that is numeric)

Metrics are the fields you want to calculate in each of these every aggregation includes a frequency metric. These are the available metric types:&#x20;

* average
* max
* min
* sum
* cardinality

To help memorise the aggregation queries, the following example can help:&#x20;

```
{
    "groupby" : [
        {"name": "region", "field": "player_region", "agg": "category"},
        {"name": "player_name", "field": "name", "agg": "category"}
    ],
    "metrics" : [
        {"name": "average_score", "field": "final_score", "agg": "avg"},
        {"name": "max_score", "field": "final_score", "agg": "max"},
        {'name':'total_score','field':"final_score", 'agg':'sum'},
        {'name':'average_deaths','field':"final_deaths", 'agg':'avg'},
        {'name':'highest_deaths','field':"final_deaths", 'agg':'max'},
    ]
}
```

In this example, we aggregate by 2 separate categories (region and player name). Based on each category, the average, max, sum of scores is calculated and the average and maximum number of deaths are calculated.&#x20;


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