Query and Projection Operator

MongoDB have a JavaScript shell that allows interaction with MongoDB instance from the command line.

If you want to create a table, you should name the table and define its column and each column's data type.

The shell is useful for performing administrative functions and running instances.

How to run the shell

To start the shell, open command prompt, run it as a administrator then run the mongo executable:

snippet
$ mongo
Output
MongoDB shell version: 2.4.0 Connecting to: test

You should start mongoDB before starting the shell because shell automatically attempt to connect to a MongoDB server on startup.

The shell is a full-featured JavaScript interpreter. It is capable of running Arbitrary JavaScript program.

Let us take a simple mathematical program:

snippet
>x= 100
100
>x/ 5;
20

You can also use the JavaScript libraries

snippet
> "Hello, World!".replace("World", "MongoDB");
Output
Hello, MongoDB!

You can even define and call JavaScript functions

snippet
> function factorial (n) {

... if (n <= 1) return 1;

... return n * factorial(n - 1);
... }

> factorial (5);

120

Note: You can create multiple commands.

When you press "Enter", the shell detect whether the JavaScript statement is complete or not.

If the statement is not completed, the shell allows you to continue writing it on the next line. If you press "Enter" three times in a row, it will cancel the half-formed command and get you back to the > - prompt.

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