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A comparison: SQL or NoSQL databases?

Aaron Xie

A database is an integral part of an application due to its ability to store, organize, and serve data. Developers are constantly trying to innovate databases to make them more efficient and powerful in order to serve the purpose of various applications. A common question that arises when choosing a database is whether to use a SQL database or NoSQL database.

SQL

SQL (Structured Query language) is the standard language for communicating with relational, table-based databases. Typically, these databases are called SQL databases. With SQL programming, you can easily search, insert, update, and delete database data.

SQL is an incredibly powerful and versatile language, which makes it a very safe choice. With SQL, you are required to pre-define schemas that structure the way your data will be organized.

Features:

  • Scalabality: SQL databases can scale vertically by adding CPU, RAM, or SSD. By adding more resources, the database can handle more load.

  • Community: SQL databases have been around for a long time, which means that they have a wide community with great documentation and support.

  • Versatile: SQL databases can be applied to a ton of data models, which makes it suitable for all types of applications. SQL also has a large collection of tools and functions that makes it very powerful.

Popular SQL databases:

  • MySQL

  • PostgreSQL

  • Microsoft SQL Server

  • Oracle Express Edition

NoSQL

NoSQL are non-relational databases, which are not structured in a table form. Most of the time, data is document-based with key-value pairs and does not have a schema.

These databases can be structured in a more flexible form since we do not need to predefine a schema. However, there’s a common misconception that NoSQL databases do not hold relationship data well. In reality, they simply create relationships differently from SQL databases.

Features:

  • Scalability: Similar to SQL databases, NoSQL databases are also easily scalable. However, they scale horizontally meaning that you add more servers to your NoSQL database. Ultimately, NoSQL scales better for larger and more powerful applications.

  • Community: NoSQL is relatively new compared to SQL databases meaning that sometimes there will be less documented support for utilizing the database. However, the popularity of NoSQL is rapidly growing in the industry.

  • Flexibility: With a NoSQL database, you are given more flexibility to store your data without a pre-defined structure, which is useful depending on the application you are building.

Popular NoSQL databases:

  • MongoDB

  • DynamoDB

  • Redis

  • RavenDB

Here are some of the main differences between SQL and NoSQL

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SQL

  • SQL databases are table based databases
  • Have predefined schema
  • Are vertically scalable
  • Use SQL (Structured Query Language) for defining and manipulating the data
  • A good fit for the complex query intensive environment
  • Emphasize ACID properties (Atomicity, Consistency, Isolation, and Durability)
  • Examples include: MySQL, Oracle, Sqlite, Postgres, and MS-SQL

NoSQL

  • NoSQL databases are document-based, key-value pairs, and graph databases
  • Have dynamic schema
  • Are horizontally scalable
  • Focused on the collection of documents
  • Not ideal for complex queries
  • Follow the Brewers CAP theorem (Consistency, Availability, and Partition tolerance)
  • Examples include: MongoDB, BigTable, Redis, RavenDb, Neo4j, and CouchDb

If you are looking to learn more about SQL databases, check out our MySQL Tutorial article, which provides an in-depth guide to MySQL.

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