SQL vs NoSQL: Key Differences and Use Cases

SQL vs NoSQL: A Comprehensive Comparison
1. Introduction
 SQL Databases: These are relational databases that use structured query
language (SQL) to manage and manipulate data. They store data in tables
with rows and columns and require a predefined schema for organizing
data.
 NoSQL Databases: These are non-relational databases designed for
handling large amounts of unstructured or semi-structured data. NoSQL
databases provide more flexibility in data models and are designed to scale
out horizontally.



2. Data Model
 SQL Databases:
o Use a relational model with tables (relations) consisting of rows and
columns. Each table has a predefined schema, meaning data must
follow a strict structure.
o Example: MySQL, PostgreSQL, Oracle
 NoSQL Databases:
o Can use various data models such as:
 Document-based: Stores data in documents (key-value pairs),
often in formats like JSON or BSON.
Example: MongoDB
 Key-value pairs: Stores data as key-value pairs, typically in
memory.
Example: Redis
 Column-family stores: Stores data in columns rather than
rows.
Example: Cassandra
 Graph-based: Stores data as nodes and edges to represent
relationships.
Example: Neo4j

, 3. Schema
 SQL Databases:
o Data must follow a strict schema, meaning you need to define the
structure of the data in advance (tables, columns, data types). Any
changes to the schema require database migrations, which can be
time-consuming.
 NoSQL Databases:
o Typically schema-less, meaning data can be stored without a
predefined structure. You can have different fields and data types in
each record, which provides flexibility for evolving data models.



4. Scalability
 SQL Databases:
o Vertical scaling (scaling up): Scaling involves adding more power
(CPU, RAM) to the existing machine. This method has limitations and
can become expensive as data grows.
 NoSQL Databases:
o Horizontal scaling (scaling out): NoSQL databases are designed for
distributed systems, meaning they can scale out by adding more
servers to distribute the data load. This allows NoSQL databases to
handle massive amounts of data and high traffic more efficiently.



5. Transactions
 SQL Databases:
o SQL databases ensure ACID (Atomicity, Consistency, Isolation,
Durability) compliance. This means transactions are processed
reliably, and data integrity is maintained even in the case of system
failures.
 NoSQL Databases:
o NoSQL databases are typically designed for high availability and
scalability, which can sometimes come at the expense of ACID