mongodb count elements in array

official website http://www.mongodb.org1, download Mongodb-win32-i386-latest.zip decompressionMongoDB 3.1.5 requires win7 to download and install memory patches HTTPS://SUPPORT.MICROSOFT.COM/ZH-CN/HOTFIX/KBHOTFIX?KBNUM=2731284KBLN=ZH-CN2, extract to

Transferred from: http://www.cnblogs.com/cswuyg/p/4355948.html1. Count Statistics result errorThis is because the distributed cluster is migrating data, which results in a count result value error and requires the use of aggregate pipeline to obtain

One, the problem description"Use unwind unpack each element in the array in Document, then use Group grouping statistics, and then sort the grouped results using sort"Import data from the Images.json file to the MongoDB serverMongoimport--drop-d

To use MongoDB, You need to import the following classes, not all of which are required.Import com. MongoDB. Mongo;Import com. MongoDB. dB;Import com. MongoDB. dbcollection;Import com. MongoDB. basicdbobject;Import com. MongoDB. dbobject;Import com.

The good point is that the database does not need to be established, after the connection, if the insertion of data operations, the system can create its own, we assume a post collection, which is a number of blog posts composed of documents. Let's

First, queryFind methodDb.collection_name.find ();Query all the results:select * from Users;Db.users.find ();Specifies that those columns (keys) are returned:Select name, skills from users;Db.users.find ({}, {' name ': 1, ' Skills ':

Mongodb advanced 2: mongodb aggregation and mongodb advanced AggregationIn the previous article we talked about mongodb's advanced query: http://blog.csdn.net/stronglyh/article/details/46817789 This article introduces mongodb aggregation. I. mongodb

The recent year is busy with data processing related work, with MongoDB very much, the following is the practice process of q&a, follow-up will not be updated regularly. 1. Count Statistics result errorThis is because the distributed cluster is

These days in the study of Python web development, so prepare to do a blog to practice practiced hand, of course, just practiced hand, blog has wordpress such a good thing, why still build their own cars? decided to use the Tornado framework, and

Brief introduction MongoDB is a NoSQL database based on distributed file storage Written by the C + + language, stable and high performance Designed to deliver scalable, high-performance data storage solutions for WEB applications