KAHIBARO
Discord Login Register ☰
☰

Introduction to PostgreSQL

Table of Contents

Why PostgreSQL Matters for Backend Development

PostgreSQL, often called “Postgres,” is a powerful open source relational database management system (RDBMS). As a backend developer, you will frequently need a reliable database to store and query application data. PostgreSQL is one of the most popular choices for modern web backends.

It is:

PostgreSQL is not the only database you can use, but it is an excellent one to learn first because it gives you strong foundations for relational databases in general.

Key idea: PostgreSQL is a relational database that uses SQL to define, store, and query data in tables.
Learning PostgreSQL teaches you practical SQL plus concepts that apply to many other relational databases.

In this chapter, you will get an overview of what makes PostgreSQL special, what you can do with it, and how you will use it in backend projects. Installation, SQL, performance tuning, and so on will be handled in later chapters, so here we focus on the big picture.

PostgreSQL in the Database Landscape

There are many relational databases: MySQL, MariaDB, SQL Server, Oracle, SQLite, and others. PostgreSQL belongs to this family but has its own philosophy.

PostgreSQL vs other relational databases

Here is a rough comparison to build intuition.

DatabaseLicenseTypical use casesStrengths
PostgreSQLOpen sourceWeb apps, analytics, geospatial, microservicesFeatures, correctness, extensibility
MySQLOpen sourceWeb apps, LAMP stack, legacy appsSimplicity, huge ecosystem
SQLitePublic domainMobile, embedded, small toolsZero config, single file, very lightweight
OracleCommercialLarge enterprises, legacy systemsEnterprise tools, long history
SQL ServerCommercial/FreeWindows shops, .NET appsIntegration with Microsoft stack

PostgreSQL focuses strongly on:

This makes it a solid default for many backend applications, from small projects to large systems.

PostgreSQL vs NoSQL databases

You will also encounter NoSQL systems like MongoDB, Cassandra, and Redis. These are often:

PostgreSQL is different because:

However, PostgreSQL has evolved and now includes features that feel “NoSQL like”, such as JSONB columns, key value style operations, and full text search. In many cases, you can keep using PostgreSQL instead of adding a second specialized database.

Core Concepts in PostgreSQL

Before using PostgreSQL in code, you need a conceptual map of its main building blocks.

Cluster, databases, schemas, and tables

PostgreSQL has a hierarchy of objects. This often confuses beginners, so keep this structure in mind:

LevelExample nameDescription
ClusterOne Postgres “server” processContains one or more databases
Databasemy_app_dbContains schemas, tables, functions, etc.
SchemapublicA namespace inside a database
TableusersStores rows of data with defined columns

In practice for simple apps:

Example mental model for a simple app:

You will learn how to actually create these in later PostgreSQL chapters.

Data types and constraints

PostgreSQL has many data types, more than many other relational databases. Some common ones you will use often:

CategoryExamples
NumericINTEGER, BIGINT, NUMERIC, REAL
TextTEXT, VARCHAR(n), CHAR(n)
BooleanBOOLEAN
Date/TimeDATE, TIME, TIMESTAMP, TIMESTAMPTZ
BinaryBYTEA
JSONJSON, JSONB
UUIDUUID

You also use constraints to enforce rules:

These make your data safer and help prevent bugs in your backend code by catching invalid data early.

Example of a table definition (simplified, you will learn syntax later):

sql 
CREATE TABLE users (
    id          SERIAL PRIMARY KEY,
    email       TEXT NOT NULL UNIQUE,
    full_name   TEXT NOT NULL,
    is_active   BOOLEAN NOT NULL DEFAULT TRUE
);

Even if you do not know all the syntax yet, you can see:

Typical PostgreSQL Use Cases in Backends

PostgreSQL supports many patterns you will see repeatedly when writing backend services.

Storing core application data

Most web apps need to store:

PostgreSQL models this with tables and relationships.

Example: a task management app:

text 
users
  id (PK)
  email
  password_hash
tasks
  id (PK)
  user_id (FK to users.id)
  title
  description
  is_completed
  created_at

You can then answer questions such as:

All with SQL queries, which we cover in the SQL section of the course.

Transactions and consistency

In real applications, you frequently need several related changes to happen atomically. For example in an ecommerce app:

  1. Create an order
  2. Reduce product inventory
  3. Save a payment record

You want either all of these steps to succeed or none of them. PostgreSQL gives you:

You will have a separate chapter focused on transactions and ACID, but for now you should understand:

In PostgreSQL you can wrap multiple database operations in a transaction so they behave as a single, all-or-nothing unit of work.

This is essential for correct backend logic.

Advanced querying and analytics

PostgreSQL supports powerful SQL features such as:

Even simple apps benefit from this. For example:

As you build more complex backends, these features become very valuable.

How Backend Code Talks to PostgreSQL

Your backend application does not talk SQL manually in a terminal in production. Instead, it connects to PostgreSQL over the network and runs queries through a driver or an ORM.

Client server model

PostgreSQL runs as a server process that listens on a port, typically 5432. Your backend application is a client:

  1. Your code opens a connection to PostgreSQL
  2. It sends SQL commands as text
  3. PostgreSQL executes them
  4. Results come back to your code

Example conceptual flow for a FastAPI endpoint:

You will learn the details of ORMs and integration in later chapters, but this is the basic idea.

Connection parameters

To connect to PostgreSQL, you usually need:

ParameterExample
Hostlocalhost
Port5432
Databasemy_app_db
Usermy_app_user
Passwordsecret_password

These are often combined into a connection URL, for example:

text 
postgresql://my_app_user:secret_password@localhost:5432/my_app_db

Your backend will use environment variables to store these values, for example:

text 
DATABASE_URL=postgresql://my_app_user:secret_password@localhost:5432/my_app_db

Then your Python code reads DATABASE_URL and uses it to connect.

Strengths and Features that Matter to Backend Developers

PostgreSQL has many advanced features. You will not use all of them on day one, but it is useful to know what is available so you can pick the right tools later.

Rich data types for real world data

Some PostgreSQL data types are especially useful in backends:

You will learn details of data types in the “PostgreSQL Data Types” chapter.

Indexes for performance

When tables grow large, queries can become slow. PostgreSQL uses indexes to speed up lookups, just like an index in a book.

Common example:

We will cover indexes in both the SQL section and the PostgreSQL section, including how they work and when to use them.

Extensions and customization

PostgreSQL is very extensible. You can add:

For most basic backends you will use the built in features only, but knowing that PostgreSQL can grow with your needs is important.

Example: Simple Application Data Model in PostgreSQL

To see PostgreSQL concepts in context, imagine a simple blog backend with:

A possible schema in PostgreSQL might look like this (simplified):

sql 
CREATE TABLE users (
    id          SERIAL PRIMARY KEY,
    email       TEXT NOT NULL UNIQUE,
    password_hash TEXT NOT NULL,
    created_at  TIMESTAMPTZ NOT NULL DEFAULT NOW()
);
CREATE TABLE posts (
    id          SERIAL PRIMARY KEY,
    user_id     INTEGER NOT NULL REFERENCES users(id),
    title       TEXT NOT NULL,
    content     TEXT NOT NULL,
    published_at TIMESTAMPTZ,
    created_at  TIMESTAMPTZ NOT NULL DEFAULT NOW()
);
CREATE TABLE comments (
    id          SERIAL PRIMARY KEY,
    post_id     INTEGER NOT NULL REFERENCES posts(id),
    user_id     INTEGER NOT NULL REFERENCES users(id),
    content     TEXT NOT NULL,
    created_at  TIMESTAMPTZ NOT NULL DEFAULT NOW()
);

Concepts in this example:

From your backend code, you could:

You will later represent these tables as Python classes when using an ORM like SQLAlchemy.

How You Will Use PostgreSQL in This Course

Throughout this course, PostgreSQL appears in several roles:

  1. Learning SQL
    • You will run CREATE, INSERT, SELECT, UPDATE, and DELETE statements against PostgreSQL.
    • You will practice joins, aggregates, indexes, and transactions.
  2. Integrating with FastAPI
    • You will connect FastAPI applications to PostgreSQL using SQLAlchemy.
    • You will build REST APIs that read and write data in PostgreSQL.
  3. Using PostgreSQL in Docker
    • You will run PostgreSQL in containers for local development.
    • You will use docker-compose to run FastAPI and PostgreSQL together.
  4. Deploying to production
    • You will configure PostgreSQL on a Linux server or use a managed PostgreSQL service.
    • You will manage migrations, backups, and performance basics.

By the end of the PostgreSQL and ORM sections, you will be comfortable:

Summary

In this chapter you learned the big picture of PostgreSQL:

Next, you will learn how to install PostgreSQL, connect to it, and start creating databases and tables that you can use from your backend code.

Views: 7

Comments

Please login to add a comment.

Don't have an account? Register now!

© 2025 Kahibaro
Visitors: 3101 / 24h
Impressum / Imprint
Datenschutz / Data Policy