Mongodb: How to do a work like `groupby` of mysql?

Question

I am using MongoDB PHP Library to malipulate mongodb data.
docs: https://docs.mongodb.com/php-library/master/tutorial/collation/#aggregation

How to do a work in mongodb like groupby of mysql?

for example,there is a collection:

    $collection=[
        ['id'=>'xxx','county'=>'Montgomery','state'=>'Alabama','abbr'=>'AL'],
        ['id'=>'xxx','county'=>'Calhoun','state'=>'Alabama','abbr'=>'AL'],
        ['id'=>'xxx','county'=>'Alameda','state'=>'California','abbr'=>'CA'],
        ['id'=>'xxx','county'=>'Butte','state'=>'California','abbr'=>'CA'],
        ['id'=>'xxx','county'=>'Baker','state'=>'Georgia','abbr'=>'GA'],
        ['id'=>'xxx','county'=>'Clarke','state'=>'Georgia','abbr'=>'GA'],
    ];

I want to get fields state and abbr,and save them into a new collection,the result is like this:

$newCollection=[
    ['id'=>'xxx','state'=>'Alabama','abbr'=>'AL'],
    ['id'=>'xxx','state'=>'California','abbr'=>'CA'],
    ['id'=>'xxx','state'=>'Georgia','abbr'=>'GA'],
];

How to do it?

what is the problem in this, do group by on state and abbr. Project only that group by element and then save in the collection using foreach. — Gopinath Navaneethan, Sep 08 '17 at 06:54

score -1 · Answer 1 · answered Sep 08 '17 at 06:52

MongoDB equivalent of the group by statement is aggregation framework (https://docs.mongodb.com/manual/reference/method/db.collection.aggregate/). Though for your requirement, if you want a new collection, you will have to use mapReduce or MongoDB views.

Mongodb: How to do a work like `groupby` of mysql?

1 Answers1