Introduction to Mongo DB finding Documents

Introduction

In this article we will learn how to find documents in mongo dB with a practical example

Previous articles have provided an introduction to mongo dB and the set up and installation, and few command line options.You can get them from the following:Introduction to Mongo Database

·         Introduction to Mongo Database

·         Introduction to Mongo DB setting up the server

·         Introduction to Mongo DB Command Line options

·         Introduction to Mongo DB install as a service

·         Introduction to Mongo DB Mongo Shell

·         Introduction to Mongo DB Replica set

·         Introduction to Mongo DB Storing Data 

·         Introduction to Mongo DB Storing Data Part 2

·         Introduction to Mongo DB Updating document

·        Introduction to Mongo DB Updating document Part2       

Objective

The objective of the article is to learn how to use the find command to retrieve documents from Mongo database.

Will take a look at Query criteria, field selection, and cursor operations

Finding Documents

Let’s have a look at the find command signature

It had a query parameter and a projection parameter. The query parameter is a filter it defines the matching criteria to run against the documents

The Projection parameter defines up those documents to which part to be returned which is optional.

We will start using the find command which we have seen in previous articles.

If our document is containing huge data and we want to retrieve only some data from it we can specify a projection to which fields we want to return as shown below...

Here our animal database contains all the animals from 1 t0 6 so now let’s find all the animals by issuing a commands shown below…

Here the gt operator means greater than and lt operator means less than

Also gte means greater equal and lte less than equal

So we can use these operators to query our database as shown above

We can also specify a range

we can also provide the matching query

Conclusion

Reference