Aggregation

If you need to get some aggregated values from a Model, you can use Model.aggregate(). Here's an example to better illustrate:

Person.aggregate({surname: "Doe"}).min("age").max("age").get(function(err,min,max){console.log("The youngest Doe guy has %d years, while the oldest is %d",min,max);});

An Array of properties can be passed to select only a few properties. An Object is also accepted to define conditions.

Here's an example to illustrate how to use .groupBy():

//The same as "select avg(weight), age from person where country='someCountry' group by age;"Person.aggregate(["age"],{country: "someCountry"}).avg("weight").groupBy("age").get(function(err,stats){// stats is an Array, each item should have 'age' and 'avg_weight'});

Base .aggregate() methods

• .limit(): you can pass a number as a limit, or two numbers as offset and limit respectively
• .order(): same as Model.find().order()

Additional .aggregate() methods

• min
• max
• avg
• sum
• count (there's a shortcut to this - Model.count)

There are more aggregate functions depending on the driver (Math functions for example).