mongodb distinct values

In the mapreduce> of data aggregation in the previous article There are three basic aggregation functions in MongoDB: count, distinct, and group. Let's take a look at these three basic aggregate functions separately.(1) CountRole: The number of

0) MONGO: Connect MongoDB database via client1) Show DBS---Display the currently created database2) Use test---Create or switch databases3) Db.dropdatabase ()--Delete the current database3) Show Collections: Displays the collection created by the

This article introduced the MongoDB in the MapReduce implementation of data aggregation method, we mentioned MongoDB in the data aggregation operation of a way--mapreduce, but in most of the day-to-day use of the process, We do not need to use

1. Count: Copy Code code as follows: --In an empty collection, Count returns a number of 0. > Db.test.count () 0 --Test the return value of count after inserting a document. > Db.test.insert ({"Test": 1}) > Db.test.count ()

MongoDB Study Notes-aggregation The latest new project to use mysql has not forgotten yet. The summary records the following MongoDB aggregation. AggregationIt refers to various operations that can process batch records and return computing results.

1. Count:--In an empty collection, Count returns a quantity of 0. > Db.test.count ()0--Test the return value of count after inserting a document.> Db.test.insert ({"Test": 1})> Db.test.count ()1> Db.test.insert ({"Test": 2})> Db.test.count

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

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

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 destinct command for MongoDB is to get a list of different values in a particular field. This command applies to normal fields, array fields, and arrays of embedded documents. MongoDB's distinct statement: Copy Code code as follows: