An Introduction to NoSQL

Thameera Senanayaka

Allion Technologies

SQL Server
MySQL
PostgreSQL
Oracle
SQLite

Databases we use

Relational Databases

Tables
Schemas & Normalization
SQL to query data

What is NoSQL?

Any database that is not a relational database
Schema-less
Running well on clusters

NoSQL !=

NoSQL ==

{
  _id: xxxxx,
  article_id: yyyy,
  time: yymmdd,
  text: abcde
}

Use Case - Comments in a blog

{
  _id: xxxxx,
  article_id: yyyy,
  time: yymmdd,
  text: abcde,
  author: {
    id: xxx,
    name: 'user'
  }
}

Use Case - Comments in a blog

{
  _id: xxxxx,
  article_id: yyyy,
  time: yymmdd,
  text: abcde,
  author: {
    id: xxx,
    name: 'user'
  },
  replies: [
    { ... },
    { ... }
  ]
}

Use Case - Comments in a blog

{
  title: 'some title',
  post: 'post',
  date: yymmdd,
  comments: [
    {
      _id: xxxxx,
      time: yymmdd,
      text: abcde,
      author: {
        id: xxx,
        name: 'user'
      },
      replies: [
        { ... },
        { ... }
      ]
    },
    {
      ...
    }
  ]
}

Types of NoSQL databases

1. Document Store

Types of NoSQL databases

2. BigTable

Types of NoSQL databases

3. Key-value store

Types of NoSQL databases

4. Graph

SQL	NoSQL
Rows	Documents
Tables	Columns
Requires a schema	Schema-less
JOINs	No JOINs (data is denormalized)
Transactional guarantees	No guarantees for multiple documents
Can be scaled (with some effort)	Excellent performance & scalability
SQL querying	JSON data object querying