SQL vs NoSQL Databases: Which is Better?

Everything you need to navigate the dilemma of choosing between SQL and NoSQL databases for your project needs.

Introduction

SQL and NoSQL databases are two distinct types of database management systems that have gained a lot of attention in recent years. While SQL (Structured Query Language) databases have traditionally been the go-to option for many applications, the rise of NoSQL (Not Only SQL or Not SQL) databases has put its superiority in question.

NoSQL databases are becoming more common due to their ability to handle enormous volumes of unstructured and semi-structured data, as well as their scalability and flexibility. NoSQL databases enable developers to take a more agile approach to data management, allowing them to adjust quickly to dynamic business demands.

In this article, we will look at the key differences between SQL and NoSQL databases, their benefits and drawbacks, real-world applications, and the significance of taking project goals into consideration when choosing between the two. So let's proceed and learn about SQL and NoSQL databases.

Understanding SQL and NoSQL databases

SQL databases, also known as relational databases, have been widely used for decades. They are based on a structured data model where data is organized into tables(rows and columns) with predefined schemas. These databases use Structured Query Language (SQL) to manage and query data.

On the other hand, NoSQL databases emerged in response to the need for handling large amounts of unstructured and semi-structured data. Unlike SQL databases, NoSQL databases do not rely on a fixed schema and provide greater flexibility in storing different types of data.

There are several types of NoSQL databases, each designed to handle specific use cases:

• Key-value stores: These databases store data as key-value pairs. They are simple and highly scalable, making them suitable for most use cases including user data storage, or even big data applications.
• Document databases: Document-oriented databases store data in flexible JSON-like documents. They are ideal for managing complex hierarchical data structures.
• Columnar databases: Columnar databases store data in columns rather than rows, enabling efficient compression and faster query performance for analytical workloads.
• Graph databases: Graph databases are designed to represent relationships between entities efficiently. They excel in scenarios where relationships play a crucial role, such as social networks or recommendation systems.

Understanding the characteristics and structure of both SQL and NoSQL databases is essential for making an informed decision about which one to use for a specific project. A graph depicting the architecture of relational and non-relational databases can be seen below:

SQL and NoSQL architectures.

Advantages and Disadvantages of SQL and NoSQL

When comparing SQL and NoSQL databases, it is important to consider the advantages and disadvantages of each. Both types of databases have their own strengths and weaknesses that make them suitable for different use cases.

SQL Databases

SQL databases have been widely used for decades and offer several advantages. Some of the key advantages of SQL databases include:

• Scalability: SQL databases excel in handling complex queries and large datasets.
• Predefined Schema: SQL databases require a predefined schema, which ensures data consistency and enforces data integrity.
• Standardization and Maturity: SQL databases have been around for a long time, resulting in a mature ecosystem with well-established standards, best practices, and community support.

However, SQL databases also have their disadvantages:

-** Limited Flexibility:** SQL databases are not well-suited for unstructured or semi-structured data since they require a predefined schema.

• Difficulty in Handling Large Datasets: Although SQL databases are scalable, handling extremely large datasets may pose challenges in terms of performance if the database is not properly optimized.

NoSQL Databases

NoSQL databases have gained popularity in recent years due to their flexibility and scalability. Some advantages of NoSQL databases include:

• Flexibility: NoSQL databases can handle unstructured and semi-structured data more effectively as they do not require a predefined schema.
• Horizontal Scalability: NoSQL databases can scale horizontally by distributing data across multiple servers.

However, NoSQL databases also have their drawbacks:

• Lack of Standardization and Maturity: The NoSQL ecosystem is still evolving, and there is no standard query language or schema design approach.
• Limited Support and Communities: Some NoSQL databases may have limited community support or lack comprehensive documentation.
• Possible Data Inconsistency: Depending on the database chosen, NoSQL databases may allow for eventual consistency, which could result in data inconsistency in certain scenarios. NoSQL databases are also based on the BASE principle, rather than the ACID principle.

Comparison between NoSQL and SQL Databases

When comparing NoSQL and SQL databases, there are several key differences that need to be considered. Let's explore these differences in more detail, here are some code examples that illustrate these differences:

Creating a Table or Collection

Here’s how to perform such a task using an SQL-based DBMS:

CREATE TABLE employees (
  id INT PRIMARY KEY,
  name VARCHAR(50),
  age INT,
  department VARCHAR(50)
);

In NoSQL (MongoDB), such a task would look like so:

db.createCollection("employees");

The code examples above demonstrate how to create a table or collection in both SQL and NoSQL databases.

In SQL, the code uses the CREATE TABLE statement to define the structure of the table. It specifies the column names, data types, and any constraints. For example, the employees' table has columns for id, name, age, and department.

In NoSQL, specifically MongoDB, the code uses the createCollection method to create a collection. Collections in NoSQL are similar to tables in SQL but with a more flexible schema. In this example, the collection name is "employees".

It's important to note that SQL databases are designed for structured data with well-defined relationships, while NoSQL databases excel at handling unstructured and semi-structured data.

Inserting Data:

To insert data using a relational DBMS, use the following query:

INSERT INTO employees (id, name, age, department)
VALUES (1, 'John Doe', 30, 'HR');

In NoSQL, the same query would look as follows (MongoDB-based example):

db.employees.insertOne({
  id: 1,
  name: 'John Doe',
  age: 30,
  department: 'HR'
});

In the code examples above, we can see how to insert data into SQL and NoSQL databases.

In SQL, the code uses the INSERT INTO statement to add a new row of data to the employees table. The column names are specified in parentheses, followed by the VALUES keyword and the corresponding values in parentheses. For example, it inserts a new employee with id 1, name 'John Doe', age 30, and department 'HR'.

In NoSQL, specifically MongoDB, the code uses the insertOne method to insert a document into the employees collection. The document is represented as a JavaScript object with key-value pairs. Each key represents a field name (e.g., id, name, age, department), and its value represents the corresponding data. In this example, it inserts a document with the same data as in SQL.

Querying Data:

In SQL, we would query data like so (we use a SELECT query for this example):

SELECT * FROM employees WHERE age > 25;

In NoSQL (MongoDB), the same query would look like this:

db.employees.find({ age: { $gt: 25 } });

In the code examples above, we can see how to query data from SQL and NoSQL databases.

In SQL, the code uses the SELECT statement to retrieve data from the employees table. The * symbol means selecting all columns, and FROM specifies the table to query from. The WHERE clause is used to filter the results based on a condition. In this example, it retrieves all rows where the age column is greater than 25.

In NoSQL, specifically MongoDB, the code uses the find method to query documents from the employees collection. The find method takes a query object as its parameter. In this example, it retrieves all documents where the age field is greater than 25, using the $gt operator.

Updating Data:

In SQL:

UPDATE employees SET department = 'Marketing' WHERE id = 1;

In NoSQL (MongoDB):

db.employees.updateOne({ id: 1 }, { $set: { department: 
'Marketing' } });

These code examples demonstrate how to update data in both SQL and NoSQL databases.

In SQL, the code uses the UPDATE statement to modify the data in the employees table. The SET keyword specifies the column to be updated and its new value. The WHERE clause is used to specify the condition for which rows should be updated. In this example, it updates the department column to 'Marketing' for the row with id = 1.

In NoSQL, specifically MongoDB, the code uses the updateOne method to update a document in the employees collection. The first parameter of the updateOne method is a query object specifying which document to update. In this example, it finds and updates the document with id = 1. The second parameter is an update object using the $set operator to specify which field(s) should be updated and their new values. In this example, it updates the department field to 'Marketing'.

Deleting Data:

In SQL, we use the DELETE query:

DELETE FROM employees WHERE id = 1;

In NoSQL (MongoDB), we use a function deleteOne (this function deletes one row – we can delete more rows using different functions):

db.employees.deleteOne({ id: 1 });

In SQL, the code uses the DELETE statement to remove data from the employees table. The WHERE clause is used to specify the condition for which rows should be deleted. In this example, it deletes the row with id = 1.

In NoSQL, specifically MongoDB, the code uses the deleteOne method to remove a document from the employees collection. The parameter of the deleteOne method is a query object specifying which document to delete. In this example, it finds and deletes the document with id = 1.

When deleting multiple rows in SQL, the query remains the same. However, In NoSQL(MongoDB), we use a function deleteMany to delete multiple documents that match a given query condition:

db.employees.deleteMany({ department:'HR' });

In this example, it deletes all documents in the employees collection where the department is HR.

These examples provide a glimpse into the syntax differences between NoSQL and SQL databases. It's important to note that the specific syntax may vary depending on the database system being used within each category (e.g., MongoDB for NoSQL). Understanding these syntax differences is crucial when working with different database solutions. It's also important to understand the project requirements and trade-offs before making a decision between NoSQL and SQL databases. The suitability of each database solution depends on factors such as data structure, scalability needs, query complexity, development speed, and ecosystem support.

Data Consistency and Transactions

Consistency is a critical aspect of database management systems, ensuring that data remains accurate and reliable. In NoSQL databases, consistency models vary depending on the database type, such as eventual consistency, strong consistency, causal consistency, or BASE (Basically Available, Soft state, Eventually consistent).

Eventual consistency allows for data to be inconsistent for a short period before eventually becoming consistent across all replicas. Strong consistency ensures immediate consistency but may impact performance and availability. Causal consistency guarantees that if one event causally precedes another, the order is maintained across replicas. BASE emphasizes availability and performance over immediate consistency.

On the other hand, SQL databases adhere to the ACID (Atomicity, Consistency, Isolation, Durability) properties to ensure transactional integrity. ACID transactions guarantee that a group of operations executes entirely or not. This ensures data remains consistent throughout the transaction and prevents partial updates.

Consistency is a critical aspect of database management systems, ensuring that data remains accurate and reliable. In NoSQL databases, consistency models vary depending on the database type, such as eventual consistency, strong consistency, or causal consistency.

There is often a trade-off between consistency and scalability in database systems. SQL databases prioritize strong consistency while sacrificing some scalability. NoSQL databases offer scalability but compromise on strong consistency. The choice between these approaches depends on the specific requirements of your project.

Understanding the nuances of data consistency models and transaction handling is crucial when deciding between NoSQL and SQL databases for your application. By carefully evaluating your project's needs, you can determine which database solution best aligns with your requirements and achieve optimal performance and reliability.

Real-world Applications

When it comes to real-world applications, both SQL and NoSQL databases have their strengths and excel in different scenarios.

SQL databases have been the traditional choice for many applications, particularly those that require strong data consistency and complex querying capabilities. Some examples of real-world applications where SQL databases excel include:

• E-commerce platforms: SQL databases are commonly used for managing product catalogs, customer data, and order processing in e-commerce platforms. The structured nature of SQL databases allows for efficient handling of transactional data.
• Banking systems: SQL databases are well-suited for financial systems that require ACID properties and strict data consistency. They are used for managing customer accounts, and transaction records and ensuring accurate balance calculations.
• Content management systems (CMS): CMS platforms often rely on SQL databases to handle structured content such as articles, user profiles, and comments. The relational model of SQL databases enables flexible querying and easy organization of content.

NoSQL databases offer flexibility and scalability advantages that make them ideal for certain types of applications. Here are examples of real-world applications where NoSQL databases excel:

• Social media platforms: NoSQL databases are commonly used in social media platforms to handle large volumes of unstructured data such as user-generated posts, comments, and social connections. The flexible schema allows for quick updates and efficient scaling.
• Internet of Things (IoT) systems: IoT applications generate massive amounts of sensor data that can be efficiently stored in NoSQL databases. The ability to handle semi-structured or unstructured data makes them a good fit for IoT use cases.
• Real-time analytics: When it comes to real-time analytics or streaming data processing, NoSQL databases shine. They can store and process vast amounts of rapidly changing data in a scalable manner.

Ecosystem and Community Support

When it comes to choosing between NoSQL and SQL databases, considering the availability of tools and frameworks, as well as the ecosystem and community support, is crucial. Both types of databases have their own set of resources that can greatly impact development and maintenance.

NoSQL databases have a growing number of tools and frameworks available to developers. These resources provide support for various aspects of database management, such as data modeling, querying, and administration. Some popular tools and frameworks for NoSQL databases include:

• MongoDB Compass: A GUI tool that allows users to interact with MongoDB databases visually.
• Cassandra Query Language (CQL): A query language specifically designed for Apache Cassandra.
• Apache Kafka: A distributed streaming platform that can be used with various NoSQL databases for real-time data processing.
• Redis CLI: A command-line interface tool for interacting with Redis databases.
• Neo4j Browser: A web-based tool for querying and visualizing graph databases.

SQL databases have been around for decades, resulting in a mature ecosystem with a wide range of tools, frameworks, and libraries. The established nature of SQL has led to extensive community support, making it easier to find solutions to common problems. Some notable resources for SQL databases include:

• MySQL Workbench: An integrated development environment (IDE) that provides tools for designing, developing, and administering MySQL databases.
• PostgreSQL Extensions: A collection of additional features and functionalities that extend the capabilities of PostgreSQL.
• Microsoft SQL Server Management Studio (SSMS): A comprehensive toolset for managing SQL Server databases.
• Oracle Application Express (APEX): A low-code development platform that simplifies building web-based applications on Oracle Database.

The availability of tools, frameworks, and community support can significantly impact the development process and ongoing maintenance of a database. Having a wide range of resources to choose from can expedite development, improve efficiency, and reduce the learning curve for developers.

Conclusion

To conclude, the debate between NoSQL and SQL databases has been ongoing for years, with both options offering unique advantages and disadvantages. Throughout this article, we have explored the characteristics, advantages, and disadvantages of each type of database.

It is important to carefully consider project requirements and trade-offs before making a decision.

NoSQL databases provide:

• BASE compliance.
• Scalability, allowing for the handling of large amounts of data and high traffic loads.
• Flexibility for unstructured and semi-structured data, accommodating various data formats.
• Better performance for specific use cases, particularly when dealing with read-heavy workloads.

SQL databases offer:

• ACID compliance.
• Standardized schemas, ensuring data consistency and integrity.
• Mature technology with a long-standing track record in the industry.
• Strong community support, with a wealth of resources and expertise available.

Understanding specific project needs is crucial in determining the suitability of each database solution. While both NoSQL and SQL databases have their strengths, the choice ultimately depends on the requirements of your particular use case.

Additionally, we've compiled a list of frequently asked questions to further assist you in making an informed decision:

FAQs

What is the main difference between NoSQL and SQL databases?

NoSQL databases provide a more flexible approach to data storage, accommodating unstructured and semi-structured data, while SQL databases adhere to structured schemas.

Which database type is better for handling large amounts of data?

NoSQL databases are generally better suited for handling large-scale data due to their horizontal scalability capabilities, but in some cases, SQL-based solutions may cut the chase - optimize your database properly, and you should be good to go.

Are SQL databases only suitable for structured data?

SQL databases are optimized for structured data, but they can handle semi-structured data through techniques like JSON storage.

Do NoSQL databases ensure data consistency?

NoSQL databases sacrifice some degree of consistency for improved scalability, offering various consistency models to choose from.

Can I migrate from one database type to another easily?

Database migrations can be complex, involving considerations like data mapping and application adjustments. The ease of migration depends on the specific case.

About the author

Ochuko Onojakpor is a full-stack Python/React software developer and freelance Technical Writer. He spends his free time contributing to open source and tutoring students on programming in collaboration with Google DSC.