Understanding SQL vs NoSQL Databases

Structured Query Language (SQL) is a domain-specific programming language commonly used for tasks such as inserting, updating, querying, and deleting data within a database. It is the common programming language used to create and manage relational databases.

Structured data is data that is organized in a consistent, predefined format and often consists of alphanumeric characters. Examples include financial transactions, inventory records, or customer lists which are often stored in SQL databases (e.g., relational databases).

Relational databases, or relational database management systems (RDBMSs), store data within rows and columns which are used to form tables. A relationship between the two tables (or more) can be created using a foreign key. These foreign keys (e.g., unique identifiers) maintain predefined relationships that exist between the tables.

Due to the fixed schema SQL databases (e.g., relational databases) use, these database systems are not able to accommodate the disparate data structures of unstructured data such as video files, photos, or text files.

Not only SQL (NoSQL) is a database management system (DBMS) approach used to ingest, store, and retrieve unstructured data and semi-structured data within a database.

Unstructured data is data that doesn't have a predefined data model or consistent organization. In addition, unstructured data, such as social media posts, can update and change rapidly while structured data, such as transactions, have a much lower rate of change. Examples of unstructured data include pictures, audio files, videos, and maps.

NoSQL databases are databases that utilize a flexible schema that accommodates unstructured data and semi-structured data while also utilizing a non-tabular data storage method.

The use of a flexible schema enables NoSQL databases to ingest unstructured data in its native format (e.g., .txt, .JPG, MP3), which is not possible with SQL databases due to the requirement that all data align to a predefined format.

The most common types of NoSQL databases include:

• Document databases
• Key-value databases
• Column-family stores
• Graph databases

The key differences between SQL databases and NoSQL databases include:

• Database storage models
• Data types
• Schemas
• Scalability