gistfile1.md

Starters guide to MongoDB

Installing MongoDB

I'll be covering how to install Mongo on Unix and Linux platform only. I don't want to bother myself with the hassles of installing Mongo on Windows OS, it's just too much work.

Presuming that you have Ruby installed, run this command in the terminal

ruby -e "$(curl -fsSL https://raw.github.com/mxcl/homebrew/go)"

Once Installed, open two terminal windows and run mongod in the first window and mongo in the second window after that. mongod will start the server and start listening for the connection on port 27017. With mongo we start the interactive JavaScript shell interface to MongoDB and run all the commands from there.

Creating a new Database

To create a new database simply run

use dataBaseName

Here dataBaseName will be the name we want to use for the database

To check all the existing collections run show collections

Creating a Collection and add inserting records to it

db.person.insert({
    first: 'Bassam',
	 last: 'Ismail',
	 dob: '19/12/1991',
	 gender: 'male',
	 country: 'Kashmir'
});

This will create a collection called person with first, last, dob, gender and location fields. I haven't created a field for the primary_key so mongo will automatically add it as every record should have a unique id.

Find Selector

Mongo has several clauses just like SQL to query specific information. The find selector is used to find specified criteria only.

Lets say we want to find all the people that are female in our person database.

db.person.find({
	gender: 'female';
});

The output that we will get will be records with gender: female fields only.

Searching for Multiple Criteria

We can query more than one record by separating multiple records using $or and placing the additional fields in [ ] and , separated.

db.person.find({
	gender: 'f', $or[{last: 'Ismail'}, {first: 'Bassam'}]
});

Sorting Records

We can sort records in MongoDB in ascending or descending order

Ascending = -1
Descending = 1

So lets say we want to get all the male fields which is all the men from the database and sort them in an ascending order by their names.

db.person.find({gender:'male'}).sort({first: -1});

We can even sort records on basis of multiple criteria as well

db.person.find({gender: 'male'}).sort({first: -1, location: 1});

Limiting Records

Incase you want to limit the result of your query to given number, Mongo can help us with it's limit selector.

Say you want to output only 3 records from your database

db.person.find({gender: 'male'}).limit(3);

Skipping Records

We can jump directly to records and skip initial one using Mongo's skip function

db.person.find({gender: 'male'}).skip(10);

This will skip the first ten records and start displaying from the eleventh one.

Updating Records

To update the fields in our database we use the update function.

db.person.update({first: 'Fouzia', last: 'Ismail'}, {$set: {gender: 'f'}});

When updating a record we have to use the $set modifier or it the record gets replaced instead of being updated.

Deleting Records

Just like everything else, deleting records from a Mongo database is walk in the park. The remove function helps us in deleting records

db.person.remove({first: 'Bilal', last: 'Ahmad'});

This will remove the record Bilal from the database. Note that there won't be any warning for this. So to check if the record has been updated and the record has been removed just db.person.find()

Incase you want to clear your database and remove all the records simply run

db.person.remove();
db.person.find();

This will remove all the records from the database and check if the database is updated for confirmation.