unwind in mongodb

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

1. Download extract MongoDB, configure environment variablesTAR-ZXVF mongodb-linux-x86_64-rhel62-3.2.7.tgzExport Path=/bin: $PATH2. Create a data Save directoryMkdir-p/data/db3.mongodb Boot./mongod//Default boot./mongod--dbpath=/data/db//Start

Heard that the project inside aggregation use more, then specifically for this a lot of practice. The basic operations include: • $project-You can extract fields from subdocuments, and you can rename fields • $match-the ability to find •

In the previous article we talked about MongoDB advanced query: http://blog.csdn.net/stronglyh/article/details/46817789This article is about MongoDB aggregation.A: MongoDB has a lot of aggregation framework, so that the transformation and

/*** MongoDB $type operator*/ /*** The $type operator is based on the Bson type to retrieve the matching data type in the collection and returns the result.* The types of MongoDB that can be used are shown in the following table:* Type Number Notes*

MongoDB database data aggregation & amp; Pipe operations, mongodb database AggregationThe data aggregation process for pipeline operations on mongodb usually works with pipeline operations. The pipeline operation concept of mongodb is similar to the

Some basics forget to check at any time.#整备恢复Mongodump--port 20001--authenticationdatabase=admin-u *-D lvlv-c lvlv-o/homeMongorestore--drop--host 172.16.201.74--port 20001--authenticationdatabase=admin-umgbackup-d test/tmp/liding/test

Start the corresponding SERVER:CD: Mongod--dbpath db Path to the Mangodb installation root directoryTo create the MANGODB service:Mongod.exe--logpath d:/mongodb/logs/mongodb.log--logappend--dbpath d:/mongodb/db--directoryperdb--serviceName

AggregationAggregate Aggregation (aggregate) is primarily used to calculate data, similar to sum (), AVG () in SQL Grammar Db. Collection name. Aggregate ([{pipe: {expression}}])Piping Pipelines are typically used in UNIX

Recently has been using MongoDB, sometimes will need to use statistics, on the Internet to check some information, the most suitable for use is to use aggregate, the following introduction of their own use of experience. MongoDB