mongodb count distinct

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

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 ()

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:--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

If you have never been familiar with MongoDB or have a little understanding of MongoDB, if you are a C # developer, take a few minutes to read this article. This article will take you step by step to get started easily. Read directory 1:

SummaryThe previous article introduced CRUD operations, which will basically do a lot of work. However, if you encounter the operation of statistical classes, then you need to learn the contents of this article.Related articlesGetting started with

Http://www.cnblogs.com/yoolonet/archive/2011/08/27/2155701.html A series of articles about MongoDB recently used MongoDB as a data storage system to record their own applications and problems in actual development. I hope this will be helpful to my

Comparison table of operations between MongoDB and MySQL and comparison table of mongodb Comparison tables and differences between MongoDB and MySQL MySQL and MongoDB are both open-source common databases, but MySQL is a traditional relational

Install MongoDB 3.0 server on CentOS71. Download and install MongoDB 3.0 official version released! This marks a new development stage for MongoDB databases, providing a powerful, flexible, and easy-to-manage database management system. MongoDB

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